ObjectDataProvider.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ Dotnetfx_Win7_3.5.1 / Dotnetfx_Win7_3.5.1 / 3.5.1 / DEVDIV / depot / DevDiv / releases / Orcas / NetFXw7 / wpf / src / Framework / System / Windows / Data / ObjectDataProvider.cs / 1 / ObjectDataProvider.cs

                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: Implementation of ObjectDataProvider object. 
// 
// Specs:       http://avalon/connecteddata/Specs/Avalon%20DataProviders.mht
// 
//---------------------------------------------------------------------------

using System;
using System.Collections; 
using System.ComponentModel;
using System.Diagnostics; 
using System.Reflection; 
using System.Windows.Threading;
using System.Threading; 
using System.Windows;
using System.Windows.Data;
using MS.Internal;
using MS.Internal.Data; // ParameterCollection 
using System.Windows.Markup;
 
//--------------------------------------------------------------------------- 
// Design notes:
// 
// ObjectDataProvider uses Activator.CreateInstance() to instantiate a new
// ObjectInstance and Type.InvokeMember() to call a member on the object.
//
// Another way to write this class is through using ConstructorInfo and 
// MethodInfo, it would allow some nice things like caching the MemberInfo
// and changing it only when the MethodParameters was changed in a 
// significant way. 
// However, it was discovered that Type.GetConstructorInfo() and
// Type.GetMethodInfo() need to know all the types of the parameters for 
// member matching.  This means that any null parameter may foil the match.
//
// By using Activator.CreateInstance() and Type.InvokeMember(), we get to
// take advantage of more of the "magic" that finds the best matched 
// constructor/method with the given parameters.
// 
// Security info: 
//
// ObjectDataProvider will fail (as it should) when it does not have 
// permissions to perform reflection on the given Type or Member.
//---------------------------------------------------------------------------

namespace System.Windows.Data 
{
    ///  
    /// The ObjectDataProvider class defines an object 
    /// that instantiates a business object for use as a source for data binding.
    ///  
    [Localizability(LocalizationCategory.NeverLocalize)] // Not localizable
    public class ObjectDataProvider : DataSourceProvider
    {
        //------------------------------------------------------ 
        //
        //  Constructors 
        // 
        //-----------------------------------------------------
 
        #region Constructors

        /// 
        /// Instantiates a new instance of a ObjectDataProvider 
        /// 
        public ObjectDataProvider() 
        { 
            _constructorParameters = new ParameterCollection(new ParameterCollectionChanged(OnParametersChanged));
            _methodParameters = new ParameterCollection(new ParameterCollectionChanged(OnParametersChanged)); 

            _sourceDataChangedHandler = new EventHandler(OnSourceDataChanged);
        }
 
        #endregion Constructors
 
        //------------------------------------------------------ 
        //
        //  Public Properties 
        //
        //------------------------------------------------------

        #region Public Properties 

        ///  
        /// The type to instantiate for use as ObjectInstance. 
        /// This is null when the ObjectDataProvider is uninitialized or explicitly set to null.
        /// If the user makes an assignment to ObjectInstance, ObjectType will return 
        /// the Type of the object (or null if the object is null).
        /// 
        /// 
        /// Only one of ObjectType or ObjectInstance can be set by the user to a non-null value. 
        /// While refresh is deferred, ObjectInstance and Data will not update until Refresh() is called.
        ///  
        public Type ObjectType 
        {
            get { return _objectType; } 
            set
            {
                // User is only allowed to set one of ObjectType or ObjectInstance.
                // To change "mode", the user must null the other property first. 
                if (_mode == SourceMode.FromInstance)
                    throw new InvalidOperationException(SR.Get(SRID.ObjectDataProviderCanHaveOnlyOneSource)); 
                _mode = (value == null) ? SourceMode.NoSource : SourceMode.FromType; 

                _constructorParameters.SetReadOnly(false); 

                if (_needNewInstance = SetObjectType(value))   // raises property changed event
                {
                    // Note: ObjectInstance and Data are not updated until Refresh() happens! 

                    if (! IsRefreshDeferred) 
                        Refresh(); 
                }
            } 
        }

        /// 
        /// This method is used by TypeDescriptor to determine if this property should 
        /// be serialized.
        ///  
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeObjectType()
        { 
            return (_mode == SourceMode.FromType) && (ObjectType != null);
        }

        ///  
        /// When ObjectType is set to a non-null value, this holds the
        /// instantiated object of the Type specified in ObjectType. 
        /// If ObjectInstance is assigned by the user, ObjectType property will reflect the Type 
        /// of the assigned object.
        /// If a DataSourceProvider is assigned to ObjectInstance, ObjectDataProvider will 
        /// use the Data of the assigned source provider as its effective ObjectInstance.
        /// 
        /// 
        /// The instance of object constructed from ObjectType and ConstructorParameters. -or- 
        /// The DataSourceProvider whose Data is used as ObjectInstance.
        ///  
        ///  
        /// Only one of ObjectType or ObjectInstance can be set by the user to a non-null value.
        /// This property, like the Data property, honors DeferRefresh: after setting the ObjectType, 
        /// ObjectInstance will not be filled until Refresh() happens.
        /// 
        public object ObjectInstance
        { 
            get
            { 
                 return (_instanceProvider != null) ? _instanceProvider : _objectInstance; 
            }
            set 
            {
                // User is only allowed to set one of ObjectType or ObjectInstance.
                // To change mode, the user must null the property first.
                if (_mode == SourceMode.FromType) 
                    throw new InvalidOperationException(SR.Get(SRID.ObjectDataProviderCanHaveOnlyOneSource));
                _mode = (value == null) ? SourceMode.NoSource : SourceMode.FromInstance; 
 
                if (ObjectInstance == value)   // instance or provider has not changed, do nothing
                { 
                    // debug-only sanity check, since GetType() isn't that cheap;
                    // using _objectInstance because we're not trying to check the type of the provider!
                    Debug.Assert((_objectInstance == null) ? (_objectType == null) : (_objectType == _objectInstance.GetType()));
                    return; 
                }
 
                if (value != null) 
                {
                    _constructorParameters.SetReadOnly(true); 
                    _constructorParameters.ClearInternal();
                }
                else
                { 
                    _constructorParameters.SetReadOnly(false);
                } 
 
                value = TryInstanceProvider(value); // returns the real instance
 
                // this also updates ObjectType if necessary:
                if (SetObjectInstance(value))   // raises property changed event
                {
                    // Note: Data is not updated until Refresh() happens! 

                    if (! IsRefreshDeferred) 
                        Refresh(); 
                }
            } 
        }

        /// 
        /// This method is used by TypeDescriptor to determine if this property should 
        /// be serialized.
        ///  
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeObjectInstance()
        { 
            return (_mode == SourceMode.FromInstance) && (ObjectInstance != null);
        }

        ///  
        /// The name of the method to call on the specified type.
        ///  
        [DefaultValue(null)] 
        public string MethodName
        { 
            get { return _methodName; }
            set
            {
                _methodName = value; 
                OnPropertyChanged(s_method);
 
                if (!IsRefreshDeferred) 
                    Refresh();
            } 
        }

        /// 
        /// Parameters to pass to the Constructor 
        /// 
        ///  
        /// Changing this collection will implicitly cause this DataProvider to refresh. 
        /// When changing multiple refresh-causing properties, the use of
        ///  is recommended. 
        /// ConstuctorParameters becomes empty and read-only when
        /// ObjectInstance is assigned a value by the user.
        /// 
        public IList ConstructorParameters 
        {
            get { return _constructorParameters; } 
        } 

        ///  
        /// This method is used by TypeDescriptor to determine if this property should
        /// be serialized.
        /// 
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeConstructorParameters()
        { 
            return (_mode == SourceMode.FromType) && (_constructorParameters.Count > 0); 
        }
 
        /// 
        /// Parameters to pass to the Method
        /// 
        ///  
        /// Changing this collection will implicitly cause this DataProvider to refresh.
        /// When changing multiple refresh-causing properties, the use of 
        ///  is recommended. 
        /// 
        public IList MethodParameters 
        {
            get { return _methodParameters; }
        }
 
        /// 
        /// This method is used by TypeDescriptor to determine if this property should 
        /// be serialized. 
        /// 
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeMethodParameters()
        {
            return _methodParameters.Count > 0;
        } 

        ///  
        /// If true object creation will be performed in a worker 
        /// thread, otherwise will be done in active context.
        ///  
        [DefaultValue(false)]
        public bool IsAsynchronous
        {
            get { return _isAsynchronous; } 
            set { _isAsynchronous = value; OnPropertyChanged(s_async); }
        } 
 
        #endregion Public Properties
 
        //-----------------------------------------------------
        //
        //  Protected Methods
        // 
        //------------------------------------------------------
 
        #region Protected Methods 

        ///  
        /// Start instantiating the requested object, either immediately
        /// or on a background thread, see IsAsynchronous.
        /// Called by base class from InitialLoad or Refresh
        ///  
        protected override void BeginQuery()
        { 
            if (TraceData.IsExtendedTraceEnabled(this, TraceDataLevel.ProviderQuery)) 
            {
                TraceData.Trace(TraceEventType.Warning, 
                                    TraceData.BeginQuery(
                                        TraceData.Identify(this),
                                        IsAsynchronous ? "asynchronous" : "synchronous"));
            } 

            if (IsAsynchronous) 
            { 
                ThreadPool.QueueUserWorkItem(new WaitCallback(QueryWorker), null);
            } 
            else
            {
                QueryWorker(null);
            } 
        }
 
        #endregion Protected Methods 

        //----------------------------------------------------- 
        //
        //  Private Methods
        //
        //----------------------------------------------------- 

        #region Private Methods 
 
        // if the passed in value was a DataSourceProvider,
        // start listening to the (new) provider, and returns the instance value; 
        // else just return the value.
        private object TryInstanceProvider(object value)
        {
            if (_instanceProvider != null)  // was using provider for source 
            {
                // stop listening to old provider 
                _instanceProvider.DataChanged -= _sourceDataChangedHandler; 
            }
 
            _instanceProvider = value as DataSourceProvider;

            if (_instanceProvider != null)
            { 
                // start listening to new provider
                _instanceProvider.DataChanged += _sourceDataChangedHandler; 
                value = _instanceProvider.Data; 
            }
 
            return value;
        }

        // called from ObjectInstance setter or from source provider data change event handler; 
        // raises property changed event;
        // return true iff ObjectInstance is changed 
        private bool SetObjectInstance(object value) 
        {
            // In FromType mode, _objectInstance is set in CreateObjectInstance() 
            Debug.Assert(_mode != SourceMode.FromType);

            if (_objectInstance == value)
                return false; 

            _objectInstance = value; 
 
            // set the objectType by looking at the new value
            SetObjectType((value != null) ? value.GetType() : null); 

            // raise this change event AFTER both oType and oInstance are updated
            OnPropertyChanged(s_instance);
 
            return true;
        } 
 
        // raises property changed event;
        // return true iff ObjectType is changed 
        private bool SetObjectType(Type newType)
        {
            if (_objectType != newType)
            { 
                _objectType = newType;
                OnPropertyChanged(s_type); 
                return true; 
            }
            return false; 
        }

        void QueryWorker(object obj)
        { 
            object      data    = null;
            Exception   e       = null; // exception to pass back to main thread 
 
            if (_mode == SourceMode.NoSource || _objectType == null)
            { 
                if (TraceData.IsEnabled)
                    TraceData.Trace(TraceEventType.Error, TraceData.ObjectDataProviderHasNoSource);
                e = new InvalidOperationException(SR.Get(SRID.ObjectDataProviderHasNoSource));
            } 
            else
            { 
                Exception exInstantiation = null; 
                if (_needNewInstance && (_mode == SourceMode.FromType))
                { 
                    // check if there are public constructors before trying to instantiate;
                    // this isn't cheap (and is redundant), but it should be better than throwing an exception.
                    ConstructorInfo[] ciAry = _objectType.GetConstructors();
                    if (ciAry.Length != 0) 
                    {
                        _objectInstance = CreateObjectInstance(out exInstantiation); 
                    } 
                    // don't try to instantiate again until type/parameters change
                    _needNewInstance = false; 
                }

                // keep going even if there's no ObjectInstance; method might be static.
 
                if (string.IsNullOrEmpty(MethodName))
                { 
                    data = _objectInstance; 
                }
                else 
                {
                    data = InvokeMethodOnInstance(out e);

                    if (e != null && exInstantiation != null) 
                    {
                        // if InvokeMethod failed, we prefer to surface the instantiation error, if any. 
                        // (although this can be confusing if the user wanted to call a static method) 
                        e = exInstantiation;
                    } 
                }
            }

            if (TraceData.IsExtendedTraceEnabled(this, TraceDataLevel.ProviderQuery)) 
            {
                TraceData.Trace(TraceEventType.Warning, 
                                    TraceData.QueryFinished( 
                                        TraceData.Identify(this),
                                        Dispatcher.CheckAccess() ? "synchronous" : "asynchronous", 
                                        TraceData.Identify(data),
                                        TraceData.IdentifyException(e)));
            }
            OnQueryFinished(data, e, null, null); 
        }
 
        object CreateObjectInstance(out Exception e) 
        {
            object  instance = null; 
            string  error   = null; // string that describes known error
            e = null;

            // PreSharp uses message numbers that the C# compiler doesn't know about. 
            // Disable the C# complaints, per the PreSharp documentation.
            #pragma warning disable 1634, 1691 
 
            // PreSharp complains about catching NullReference (and other) exceptions.
            // It doesn't recognize that IsCriticalException() handles these correctly. 
            #pragma warning disable 56500

            Debug.Assert(_objectType != null);
 
            try
            { 
                object[] parameters = new object[_constructorParameters.Count]; 
                _constructorParameters.CopyTo(parameters, 0);
                instance = Activator.CreateInstance(_objectType, 0, null, parameters, 
                                System.Globalization.CultureInfo.InvariantCulture);
                OnPropertyChanged(s_instance);
            }
            catch (ArgumentException ae) 
            {
                // this may fire when trying to create Context Affinity objects 
                error = "Cannot create Context Affinity object."; 
                e = ae;
            } 
            catch (System.Runtime.InteropServices.COMException ce)
            {
                // this may fire due to marshalling issues
                error = "Marshaling issue detected."; 
                e = ce;
            } 
            catch (System.MissingMethodException mme) 
            {
                // this may be due to setting parameters to a non parameter 
                // only class contructor
                error = "Wrong parameters for constructor.";
                e = mme;
            } 
            // Catch all exceptions.  When there is no app code on the stack,
            // the exception isn't actionable by the app. 
            // Yet we don't want to crash the app. 
            catch (Exception ex)
            { 
                if (CriticalExceptions.IsCriticalException(ex))
                    throw;
                error = null;   // indicate unknown error
                e = ex; 
            }
            catch // non CLS compliant exception 
            { 
                error = null;   // indicate unknown error
                e = new InvalidOperationException(SR.Get(SRID.ObjectDataProviderNonCLSException, _objectType.Name)); 
            }

            #pragma warning restore 56500
            #pragma warning restore 1634, 1691 

            if (e != null || error != null) 
            { 
                // report known errors through TraceData (instead of throwing exceptions)
                if (TraceData.IsEnabled) 
                    TraceData.Trace(TraceEventType.Error, TraceData.ObjDPCreateFailed, _objectType.Name, error, e);

                // in async mode we pass all exceptions to main thread;
                // in [....] mode we don't handle unknown exceptions. 
                if (!IsAsynchronous && error == null)
                    throw e; 
            } 

            return instance; 
        }

        object InvokeMethodOnInstance(out Exception e)
        { 
            object  data = null;
            string  error   = null; // string that describes known error 
            e = null; 

            Debug.Assert(_objectType != null); 

            object[] parameters = new object[_methodParameters.Count];
            _methodParameters.CopyTo(parameters, 0);
 
            // PreSharp uses message numbers that the C# compiler doesn't know about.
            // Disable the C# complaints, per the PreSharp documentation. 
            #pragma warning disable 1634, 1691 

            // PreSharp complains about catching NullReference (and other) exceptions. 
            // It doesn't recognize that IsCriticalException() handles these correctly.
            #pragma warning disable 56500

            try 
            {
                data = _objectType.InvokeMember(MethodName, 
                    s_invokeMethodFlags, null, _objectInstance, parameters, 
                    System.Globalization.CultureInfo.InvariantCulture);
            } 
            catch (ArgumentException ae)
            {
                error = "Parameter array contains a string that is a null reference.";
                e = ae; 
            }
            catch (MethodAccessException mae) 
            { 
                error = "The specified member is a class initializer.";
                e = mae; 
            }
            catch (MissingMethodException mme)
            {
                error = "No method was found with matching parameter signature."; 
                e = mme;
            } 
            catch (TargetException te) 
            {
                error = "The specified member cannot be invoked on target."; 
                e = te;
            }
            catch (AmbiguousMatchException ame)
            { 
                error = "More than one method matches the binding criteria.";
                e = ame; 
            } 
            // Catch all exceptions.  When there is no app code on the stack,
            // the exception isn't actionable by the app. 
            // Yet we don't want to crash the app.
            catch (Exception ex)
            {
                if (CriticalExceptions.IsCriticalException(ex)) 
                {
                    throw; 
                } 
                error = null;   // indicate unknown error
                e = ex; 
            }
            catch   //FXCop Fix: CatchNonClsCompliantExceptionsInGeneralHandlers
            {
                error = null;   // indicate unknown error 
                e = new InvalidOperationException(SR.Get(SRID.ObjectDataProviderNonCLSExceptionInvoke, MethodName, _objectType.Name));
            } 
 
            #pragma warning restore 56500
            #pragma warning restore 1634, 1691 

            if (e != null || error != null)
            {
                // report known errors through TraceData (instead of throwing exceptions) 
                if (TraceData.IsEnabled)
                    TraceData.Trace(TraceEventType.Error, TraceData.ObjDPInvokeFailed, MethodName, _objectType.Name, error, e); 
 
                // in async mode we pass all exceptions to main thread;
                // in [....] mode we don't handle unknown exceptions. 
                if (!IsAsynchronous && error == null)
                    throw e;
            }
 
            return data;
        } 
 
        // call-back function for the ParameterCollections
        private void OnParametersChanged(ParameterCollection sender) 
        {
            // if the ConstructorParameters change, remember to instantiate a new object
            if (sender == _constructorParameters)
            { 
                // sanity check: we shouldn't have ctor param changes in FromInstance mode
                Invariant.Assert (_mode != SourceMode.FromInstance); 
 
                _needNewInstance = true;
            } 

            // Note: ObjectInstance and Data are not updated until Refresh() happens!

            if (!IsRefreshDeferred) 
                Refresh();
        } 
 
        // handler for DataChanged event of the instance's DataSourceProvider
        private void OnSourceDataChanged(object sender, EventArgs args) 
        {
            Invariant.Assert(sender == _instanceProvider);

            if (SetObjectInstance(_instanceProvider.Data)) 
            {
                // Note: Data is not updated until Refresh() happens! 
 
                if (! IsRefreshDeferred)
                    Refresh(); 
            }
        }

        ///  
        /// Helper to raise a PropertyChanged event  />).
        ///  
        private void OnPropertyChanged(string propertyName) 
        {
            OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); 
        }

        #endregion Private Methods
 
        //-----------------------------------------------------
        // 
        //  Private Types 
        //
        //------------------------------------------------------ 

        #region Private Types

        private enum SourceMode 
        {
            NoSource,           // can accept assignment to ObjectType or ObjectSource 
            FromType,           // can accept assignment only to ObjectType 
            FromInstance,   // can accept assignment only to ObjectInstance
        } 

        #endregion Private Types

        //----------------------------------------------------- 
        //
        //  Private Fields 
        // 
        //------------------------------------------------------
 
        #region Private Fields

        Type _objectType;
        object _objectInstance; 
        string _methodName;
        DataSourceProvider _instanceProvider; 
        ParameterCollection _constructorParameters; 
        ParameterCollection _methodParameters;
        bool _isAsynchronous = false; 

        SourceMode _mode = SourceMode.NoSource;
        bool _needNewInstance = true;   // set to true when ObjectType or ConstructorParameters change
 
        EventHandler _sourceDataChangedHandler;
 
        const string s_instance = "ObjectInstance"; 
        const string s_type = "ObjectType";
        const string s_method = "MethodName"; 
        const string s_async = "IsAsynchronous";
        const BindingFlags s_invokeMethodFlags =
                            BindingFlags.Public |
                            BindingFlags.Instance | 
                            BindingFlags.Static |
                            BindingFlags.InvokeMethod | 
                            BindingFlags.FlattenHierarchy | 
                            BindingFlags.OptionalParamBinding;
 
        #endregion Private Fields
    }
}
 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
//---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: Implementation of ObjectDataProvider object. 
// 
// Specs:       http://avalon/connecteddata/Specs/Avalon%20DataProviders.mht
// 
//---------------------------------------------------------------------------

using System;
using System.Collections; 
using System.ComponentModel;
using System.Diagnostics; 
using System.Reflection; 
using System.Windows.Threading;
using System.Threading; 
using System.Windows;
using System.Windows.Data;
using MS.Internal;
using MS.Internal.Data; // ParameterCollection 
using System.Windows.Markup;
 
//--------------------------------------------------------------------------- 
// Design notes:
// 
// ObjectDataProvider uses Activator.CreateInstance() to instantiate a new
// ObjectInstance and Type.InvokeMember() to call a member on the object.
//
// Another way to write this class is through using ConstructorInfo and 
// MethodInfo, it would allow some nice things like caching the MemberInfo
// and changing it only when the MethodParameters was changed in a 
// significant way. 
// However, it was discovered that Type.GetConstructorInfo() and
// Type.GetMethodInfo() need to know all the types of the parameters for 
// member matching.  This means that any null parameter may foil the match.
//
// By using Activator.CreateInstance() and Type.InvokeMember(), we get to
// take advantage of more of the "magic" that finds the best matched 
// constructor/method with the given parameters.
// 
// Security info: 
//
// ObjectDataProvider will fail (as it should) when it does not have 
// permissions to perform reflection on the given Type or Member.
//---------------------------------------------------------------------------

namespace System.Windows.Data 
{
    ///  
    /// The ObjectDataProvider class defines an object 
    /// that instantiates a business object for use as a source for data binding.
    ///  
    [Localizability(LocalizationCategory.NeverLocalize)] // Not localizable
    public class ObjectDataProvider : DataSourceProvider
    {
        //------------------------------------------------------ 
        //
        //  Constructors 
        // 
        //-----------------------------------------------------
 
        #region Constructors

        /// 
        /// Instantiates a new instance of a ObjectDataProvider 
        /// 
        public ObjectDataProvider() 
        { 
            _constructorParameters = new ParameterCollection(new ParameterCollectionChanged(OnParametersChanged));
            _methodParameters = new ParameterCollection(new ParameterCollectionChanged(OnParametersChanged)); 

            _sourceDataChangedHandler = new EventHandler(OnSourceDataChanged);
        }
 
        #endregion Constructors
 
        //------------------------------------------------------ 
        //
        //  Public Properties 
        //
        //------------------------------------------------------

        #region Public Properties 

        ///  
        /// The type to instantiate for use as ObjectInstance. 
        /// This is null when the ObjectDataProvider is uninitialized or explicitly set to null.
        /// If the user makes an assignment to ObjectInstance, ObjectType will return 
        /// the Type of the object (or null if the object is null).
        /// 
        /// 
        /// Only one of ObjectType or ObjectInstance can be set by the user to a non-null value. 
        /// While refresh is deferred, ObjectInstance and Data will not update until Refresh() is called.
        ///  
        public Type ObjectType 
        {
            get { return _objectType; } 
            set
            {
                // User is only allowed to set one of ObjectType or ObjectInstance.
                // To change "mode", the user must null the other property first. 
                if (_mode == SourceMode.FromInstance)
                    throw new InvalidOperationException(SR.Get(SRID.ObjectDataProviderCanHaveOnlyOneSource)); 
                _mode = (value == null) ? SourceMode.NoSource : SourceMode.FromType; 

                _constructorParameters.SetReadOnly(false); 

                if (_needNewInstance = SetObjectType(value))   // raises property changed event
                {
                    // Note: ObjectInstance and Data are not updated until Refresh() happens! 

                    if (! IsRefreshDeferred) 
                        Refresh(); 
                }
            } 
        }

        /// 
        /// This method is used by TypeDescriptor to determine if this property should 
        /// be serialized.
        ///  
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeObjectType()
        { 
            return (_mode == SourceMode.FromType) && (ObjectType != null);
        }

        ///  
        /// When ObjectType is set to a non-null value, this holds the
        /// instantiated object of the Type specified in ObjectType. 
        /// If ObjectInstance is assigned by the user, ObjectType property will reflect the Type 
        /// of the assigned object.
        /// If a DataSourceProvider is assigned to ObjectInstance, ObjectDataProvider will 
        /// use the Data of the assigned source provider as its effective ObjectInstance.
        /// 
        /// 
        /// The instance of object constructed from ObjectType and ConstructorParameters. -or- 
        /// The DataSourceProvider whose Data is used as ObjectInstance.
        ///  
        ///  
        /// Only one of ObjectType or ObjectInstance can be set by the user to a non-null value.
        /// This property, like the Data property, honors DeferRefresh: after setting the ObjectType, 
        /// ObjectInstance will not be filled until Refresh() happens.
        /// 
        public object ObjectInstance
        { 
            get
            { 
                 return (_instanceProvider != null) ? _instanceProvider : _objectInstance; 
            }
            set 
            {
                // User is only allowed to set one of ObjectType or ObjectInstance.
                // To change mode, the user must null the property first.
                if (_mode == SourceMode.FromType) 
                    throw new InvalidOperationException(SR.Get(SRID.ObjectDataProviderCanHaveOnlyOneSource));
                _mode = (value == null) ? SourceMode.NoSource : SourceMode.FromInstance; 
 
                if (ObjectInstance == value)   // instance or provider has not changed, do nothing
                { 
                    // debug-only sanity check, since GetType() isn't that cheap;
                    // using _objectInstance because we're not trying to check the type of the provider!
                    Debug.Assert((_objectInstance == null) ? (_objectType == null) : (_objectType == _objectInstance.GetType()));
                    return; 
                }
 
                if (value != null) 
                {
                    _constructorParameters.SetReadOnly(true); 
                    _constructorParameters.ClearInternal();
                }
                else
                { 
                    _constructorParameters.SetReadOnly(false);
                } 
 
                value = TryInstanceProvider(value); // returns the real instance
 
                // this also updates ObjectType if necessary:
                if (SetObjectInstance(value))   // raises property changed event
                {
                    // Note: Data is not updated until Refresh() happens! 

                    if (! IsRefreshDeferred) 
                        Refresh(); 
                }
            } 
        }

        /// 
        /// This method is used by TypeDescriptor to determine if this property should 
        /// be serialized.
        ///  
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeObjectInstance()
        { 
            return (_mode == SourceMode.FromInstance) && (ObjectInstance != null);
        }

        ///  
        /// The name of the method to call on the specified type.
        ///  
        [DefaultValue(null)] 
        public string MethodName
        { 
            get { return _methodName; }
            set
            {
                _methodName = value; 
                OnPropertyChanged(s_method);
 
                if (!IsRefreshDeferred) 
                    Refresh();
            } 
        }

        /// 
        /// Parameters to pass to the Constructor 
        /// 
        ///  
        /// Changing this collection will implicitly cause this DataProvider to refresh. 
        /// When changing multiple refresh-causing properties, the use of
        ///  is recommended. 
        /// ConstuctorParameters becomes empty and read-only when
        /// ObjectInstance is assigned a value by the user.
        /// 
        public IList ConstructorParameters 
        {
            get { return _constructorParameters; } 
        } 

        ///  
        /// This method is used by TypeDescriptor to determine if this property should
        /// be serialized.
        /// 
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeConstructorParameters()
        { 
            return (_mode == SourceMode.FromType) && (_constructorParameters.Count > 0); 
        }
 
        /// 
        /// Parameters to pass to the Method
        /// 
        ///  
        /// Changing this collection will implicitly cause this DataProvider to refresh.
        /// When changing multiple refresh-causing properties, the use of 
        ///  is recommended. 
        /// 
        public IList MethodParameters 
        {
            get { return _methodParameters; }
        }
 
        /// 
        /// This method is used by TypeDescriptor to determine if this property should 
        /// be serialized. 
        /// 
        [EditorBrowsable(EditorBrowsableState.Never)] 
        public bool ShouldSerializeMethodParameters()
        {
            return _methodParameters.Count > 0;
        } 

        ///  
        /// If true object creation will be performed in a worker 
        /// thread, otherwise will be done in active context.
        ///  
        [DefaultValue(false)]
        public bool IsAsynchronous
        {
            get { return _isAsynchronous; } 
            set { _isAsynchronous = value; OnPropertyChanged(s_async); }
        } 
 
        #endregion Public Properties
 
        //-----------------------------------------------------
        //
        //  Protected Methods
        // 
        //------------------------------------------------------
 
        #region Protected Methods 

        ///  
        /// Start instantiating the requested object, either immediately
        /// or on a background thread, see IsAsynchronous.
        /// Called by base class from InitialLoad or Refresh
        ///  
        protected override void BeginQuery()
        { 
            if (TraceData.IsExtendedTraceEnabled(this, TraceDataLevel.ProviderQuery)) 
            {
                TraceData.Trace(TraceEventType.Warning, 
                                    TraceData.BeginQuery(
                                        TraceData.Identify(this),
                                        IsAsynchronous ? "asynchronous" : "synchronous"));
            } 

            if (IsAsynchronous) 
            { 
                ThreadPool.QueueUserWorkItem(new WaitCallback(QueryWorker), null);
            } 
            else
            {
                QueryWorker(null);
            } 
        }
 
        #endregion Protected Methods 

        //----------------------------------------------------- 
        //
        //  Private Methods
        //
        //----------------------------------------------------- 

        #region Private Methods 
 
        // if the passed in value was a DataSourceProvider,
        // start listening to the (new) provider, and returns the instance value; 
        // else just return the value.
        private object TryInstanceProvider(object value)
        {
            if (_instanceProvider != null)  // was using provider for source 
            {
                // stop listening to old provider 
                _instanceProvider.DataChanged -= _sourceDataChangedHandler; 
            }
 
            _instanceProvider = value as DataSourceProvider;

            if (_instanceProvider != null)
            { 
                // start listening to new provider
                _instanceProvider.DataChanged += _sourceDataChangedHandler; 
                value = _instanceProvider.Data; 
            }
 
            return value;
        }

        // called from ObjectInstance setter or from source provider data change event handler; 
        // raises property changed event;
        // return true iff ObjectInstance is changed 
        private bool SetObjectInstance(object value) 
        {
            // In FromType mode, _objectInstance is set in CreateObjectInstance() 
            Debug.Assert(_mode != SourceMode.FromType);

            if (_objectInstance == value)
                return false; 

            _objectInstance = value; 
 
            // set the objectType by looking at the new value
            SetObjectType((value != null) ? value.GetType() : null); 

            // raise this change event AFTER both oType and oInstance are updated
            OnPropertyChanged(s_instance);
 
            return true;
        } 
 
        // raises property changed event;
        // return true iff ObjectType is changed 
        private bool SetObjectType(Type newType)
        {
            if (_objectType != newType)
            { 
                _objectType = newType;
                OnPropertyChanged(s_type); 
                return true; 
            }
            return false; 
        }

        void QueryWorker(object obj)
        { 
            object      data    = null;
            Exception   e       = null; // exception to pass back to main thread 
 
            if (_mode == SourceMode.NoSource || _objectType == null)
            { 
                if (TraceData.IsEnabled)
                    TraceData.Trace(TraceEventType.Error, TraceData.ObjectDataProviderHasNoSource);
                e = new InvalidOperationException(SR.Get(SRID.ObjectDataProviderHasNoSource));
            } 
            else
            { 
                Exception exInstantiation = null; 
                if (_needNewInstance && (_mode == SourceMode.FromType))
                { 
                    // check if there are public constructors before trying to instantiate;
                    // this isn't cheap (and is redundant), but it should be better than throwing an exception.
                    ConstructorInfo[] ciAry = _objectType.GetConstructors();
                    if (ciAry.Length != 0) 
                    {
                        _objectInstance = CreateObjectInstance(out exInstantiation); 
                    } 
                    // don't try to instantiate again until type/parameters change
                    _needNewInstance = false; 
                }

                // keep going even if there's no ObjectInstance; method might be static.
 
                if (string.IsNullOrEmpty(MethodName))
                { 
                    data = _objectInstance; 
                }
                else 
                {
                    data = InvokeMethodOnInstance(out e);

                    if (e != null && exInstantiation != null) 
                    {
                        // if InvokeMethod failed, we prefer to surface the instantiation error, if any. 
                        // (although this can be confusing if the user wanted to call a static method) 
                        e = exInstantiation;
                    } 
                }
            }

            if (TraceData.IsExtendedTraceEnabled(this, TraceDataLevel.ProviderQuery)) 
            {
                TraceData.Trace(TraceEventType.Warning, 
                                    TraceData.QueryFinished( 
                                        TraceData.Identify(this),
                                        Dispatcher.CheckAccess() ? "synchronous" : "asynchronous", 
                                        TraceData.Identify(data),
                                        TraceData.IdentifyException(e)));
            }
            OnQueryFinished(data, e, null, null); 
        }
 
        object CreateObjectInstance(out Exception e) 
        {
            object  instance = null; 
            string  error   = null; // string that describes known error
            e = null;

            // PreSharp uses message numbers that the C# compiler doesn't know about. 
            // Disable the C# complaints, per the PreSharp documentation.
            #pragma warning disable 1634, 1691 
 
            // PreSharp complains about catching NullReference (and other) exceptions.
            // It doesn't recognize that IsCriticalException() handles these correctly. 
            #pragma warning disable 56500

            Debug.Assert(_objectType != null);
 
            try
            { 
                object[] parameters = new object[_constructorParameters.Count]; 
                _constructorParameters.CopyTo(parameters, 0);
                instance = Activator.CreateInstance(_objectType, 0, null, parameters, 
                                System.Globalization.CultureInfo.InvariantCulture);
                OnPropertyChanged(s_instance);
            }
            catch (ArgumentException ae) 
            {
                // this may fire when trying to create Context Affinity objects 
                error = "Cannot create Context Affinity object."; 
                e = ae;
            } 
            catch (System.Runtime.InteropServices.COMException ce)
            {
                // this may fire due to marshalling issues
                error = "Marshaling issue detected."; 
                e = ce;
            } 
            catch (System.MissingMethodException mme) 
            {
                // this may be due to setting parameters to a non parameter 
                // only class contructor
                error = "Wrong parameters for constructor.";
                e = mme;
            } 
            // Catch all exceptions.  When there is no app code on the stack,
            // the exception isn't actionable by the app. 
            // Yet we don't want to crash the app. 
            catch (Exception ex)
            { 
                if (CriticalExceptions.IsCriticalException(ex))
                    throw;
                error = null;   // indicate unknown error
                e = ex; 
            }
            catch // non CLS compliant exception 
            { 
                error = null;   // indicate unknown error
                e = new InvalidOperationException(SR.Get(SRID.ObjectDataProviderNonCLSException, _objectType.Name)); 
            }

            #pragma warning restore 56500
            #pragma warning restore 1634, 1691 

            if (e != null || error != null) 
            { 
                // report known errors through TraceData (instead of throwing exceptions)
                if (TraceData.IsEnabled) 
                    TraceData.Trace(TraceEventType.Error, TraceData.ObjDPCreateFailed, _objectType.Name, error, e);

                // in async mode we pass all exceptions to main thread;
                // in [....] mode we don't handle unknown exceptions. 
                if (!IsAsynchronous && error == null)
                    throw e; 
            } 

            return instance; 
        }

        object InvokeMethodOnInstance(out Exception e)
        { 
            object  data = null;
            string  error   = null; // string that describes known error 
            e = null; 

            Debug.Assert(_objectType != null); 

            object[] parameters = new object[_methodParameters.Count];
            _methodParameters.CopyTo(parameters, 0);
 
            // PreSharp uses message numbers that the C# compiler doesn't know about.
            // Disable the C# complaints, per the PreSharp documentation. 
            #pragma warning disable 1634, 1691 

            // PreSharp complains about catching NullReference (and other) exceptions. 
            // It doesn't recognize that IsCriticalException() handles these correctly.
            #pragma warning disable 56500

            try 
            {
                data = _objectType.InvokeMember(MethodName, 
                    s_invokeMethodFlags, null, _objectInstance, parameters, 
                    System.Globalization.CultureInfo.InvariantCulture);
            } 
            catch (ArgumentException ae)
            {
                error = "Parameter array contains a string that is a null reference.";
                e = ae; 
            }
            catch (MethodAccessException mae) 
            { 
                error = "The specified member is a class initializer.";
                e = mae; 
            }
            catch (MissingMethodException mme)
            {
                error = "No method was found with matching parameter signature."; 
                e = mme;
            } 
            catch (TargetException te) 
            {
                error = "The specified member cannot be invoked on target."; 
                e = te;
            }
            catch (AmbiguousMatchException ame)
            { 
                error = "More than one method matches the binding criteria.";
                e = ame; 
            } 
            // Catch all exceptions.  When there is no app code on the stack,
            // the exception isn't actionable by the app. 
            // Yet we don't want to crash the app.
            catch (Exception ex)
            {
                if (CriticalExceptions.IsCriticalException(ex)) 
                {
                    throw; 
                } 
                error = null;   // indicate unknown error
                e = ex; 
            }
            catch   //FXCop Fix: CatchNonClsCompliantExceptionsInGeneralHandlers
            {
                error = null;   // indicate unknown error 
                e = new InvalidOperationException(SR.Get(SRID.ObjectDataProviderNonCLSExceptionInvoke, MethodName, _objectType.Name));
            } 
 
            #pragma warning restore 56500
            #pragma warning restore 1634, 1691 

            if (e != null || error != null)
            {
                // report known errors through TraceData (instead of throwing exceptions) 
                if (TraceData.IsEnabled)
                    TraceData.Trace(TraceEventType.Error, TraceData.ObjDPInvokeFailed, MethodName, _objectType.Name, error, e); 
 
                // in async mode we pass all exceptions to main thread;
                // in [....] mode we don't handle unknown exceptions. 
                if (!IsAsynchronous && error == null)
                    throw e;
            }
 
            return data;
        } 
 
        // call-back function for the ParameterCollections
        private void OnParametersChanged(ParameterCollection sender) 
        {
            // if the ConstructorParameters change, remember to instantiate a new object
            if (sender == _constructorParameters)
            { 
                // sanity check: we shouldn't have ctor param changes in FromInstance mode
                Invariant.Assert (_mode != SourceMode.FromInstance); 
 
                _needNewInstance = true;
            } 

            // Note: ObjectInstance and Data are not updated until Refresh() happens!

            if (!IsRefreshDeferred) 
                Refresh();
        } 
 
        // handler for DataChanged event of the instance's DataSourceProvider
        private void OnSourceDataChanged(object sender, EventArgs args) 
        {
            Invariant.Assert(sender == _instanceProvider);

            if (SetObjectInstance(_instanceProvider.Data)) 
            {
                // Note: Data is not updated until Refresh() happens! 
 
                if (! IsRefreshDeferred)
                    Refresh(); 
            }
        }

        ///  
        /// Helper to raise a PropertyChanged event  />).
        ///  
        private void OnPropertyChanged(string propertyName) 
        {
            OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); 
        }

        #endregion Private Methods
 
        //-----------------------------------------------------
        // 
        //  Private Types 
        //
        //------------------------------------------------------ 

        #region Private Types

        private enum SourceMode 
        {
            NoSource,           // can accept assignment to ObjectType or ObjectSource 
            FromType,           // can accept assignment only to ObjectType 
            FromInstance,   // can accept assignment only to ObjectInstance
        } 

        #endregion Private Types

        //----------------------------------------------------- 
        //
        //  Private Fields 
        // 
        //------------------------------------------------------
 
        #region Private Fields

        Type _objectType;
        object _objectInstance; 
        string _methodName;
        DataSourceProvider _instanceProvider; 
        ParameterCollection _constructorParameters; 
        ParameterCollection _methodParameters;
        bool _isAsynchronous = false; 

        SourceMode _mode = SourceMode.NoSource;
        bool _needNewInstance = true;   // set to true when ObjectType or ConstructorParameters change
 
        EventHandler _sourceDataChangedHandler;
 
        const string s_instance = "ObjectInstance"; 
        const string s_type = "ObjectType";
        const string s_method = "MethodName"; 
        const string s_async = "IsAsynchronous";
        const BindingFlags s_invokeMethodFlags =
                            BindingFlags.Public |
                            BindingFlags.Instance | 
                            BindingFlags.Static |
                            BindingFlags.InvokeMethod | 
                            BindingFlags.FlattenHierarchy | 
                            BindingFlags.OptionalParamBinding;
 
        #endregion Private Fields
    }
}
 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
                        

Link Menu

Network programming in C#, Network Programming in VB.NET, Network Programming in .NET
This book is available now!
Buy at Amazon US or
Buy at Amazon UK