DataBoundControl.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / xsp / System / Web / UI / WebControls / DataBoundControl.cs / 1305376 / DataBoundControl.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    using System.Web.Util;
    using System.Web.UI.WebControls.Adapters;
 

    ///  
    /// A DataBoundControl is bound to a data source and generates its 
    /// user interface (or child control hierarchy typically), by enumerating
    /// the items in the data source it is bound to. 
    /// DataBoundControl is an abstract base class that defines the common
    /// characteristics of all controls that use a list as a data source, such as
    /// DataGrid, DataBoundTable, ListBox etc. It encapsulates the logic
    /// of how a data-bound control binds to collections or DataControl instances. 
    /// 
 
    [ 
    Designer("System.Web.UI.Design.WebControls.DataBoundControlDesigner, " + AssemblyRef.SystemDesign),
    ] 
    public abstract class DataBoundControl : BaseDataBoundControl {

        private DataSourceView _currentView;
        private bool _currentViewIsFromDataSourceID; 
        private bool _currentViewValid;
        private IDataSource _currentDataSource; 
        private bool _currentDataSourceValid; 
        private DataSourceSelectArguments _arguments;
        private bool _pagePreLoadFired; 
        private bool _ignoreDataSourceViewChanged;

        private const string DataBoundViewStateKey = "_!DataBound";
 

        ///  
        /// The name of the list that the DataBoundControl should bind to when 
        /// its data source contains more than one list of data items.
        ///  
        [
        DefaultValue(""),
        Themeable(false),
        WebCategory("Data"), 
        WebSysDescription(SR.DataBoundControl_DataMember)
        ] 
        public virtual string DataMember { 
            get {
                object o = ViewState["DataMember"]; 
                if (o != null) {
                    return (string)o;
                }
                return String.Empty; 
            }
            set { 
                ViewState["DataMember"] = value; 
                OnDataPropertyChanged();
            } 
        }


        ///  
        [
        IDReferenceProperty(typeof(DataSourceControl)) 
        ] 
        public override string DataSourceID {
            get { 
                return base.DataSourceID;
            }
            set {
                base.DataSourceID = value; 
            }
        } 
 
        [
        Browsable(false), 
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)
        ]
        public IDataSource DataSourceObject {
            get { 
                return GetDataSource();
            } 
        } 

        protected DataSourceSelectArguments SelectArguments { 
            get {
                if (_arguments == null) {
                    _arguments = CreateDataSourceSelectArguments();
                } 
                return _arguments;
            } 
        } 

        ///  
        /// Connects this data bound control to the appropriate DataSourceView
        /// and hooks up the appropriate event listener for the
        /// DataSourceViewChanged event. The return value is the new view (if
        /// any) that was connected to. An exception is thrown if there is 
        /// a problem finding the requested view or data source.
        ///  
        private DataSourceView ConnectToDataSourceView() { 
            if (_currentViewValid && !DesignMode) {
                // If the current view is correct, there is no need to reconnect 
                return _currentView;
            }

            // Disconnect from old view, if necessary 
            if ((_currentView != null) && (_currentViewIsFromDataSourceID)) {
                // We only care about this event if we are bound through the DataSourceID property 
                _currentView.DataSourceViewChanged -= new EventHandler(OnDataSourceViewChanged); 
            }
 
            // Connect to new view
            _currentDataSource = GetDataSource();
            string dataMember = DataMember;
 
            if (_currentDataSource == null) {
                // DataSource control was not found, construct a temporary data source to wrap the data 
                _currentDataSource = new ReadOnlyDataSource(DataSource, dataMember); 
            }
            else { 
                // Ensure that both DataSourceID as well as DataSource are not set at the same time
                if (DataSource != null) {
                    throw new InvalidOperationException(SR.GetString(SR.DataControl_MultipleDataSources, ID));
                } 
            }
            _currentDataSourceValid = true; 
 
            // IDataSource was found, extract the appropriate view and return it
            DataSourceView newView = _currentDataSource.GetView(dataMember); 
            if (newView == null) {
                throw new InvalidOperationException(SR.GetString(SR.DataControl_ViewNotFound, ID));
            }
 
            _currentViewIsFromDataSourceID = IsBoundUsingDataSourceID;
            _currentView = newView; 
            if ((_currentView != null) && (_currentViewIsFromDataSourceID)) { 
                // We only care about this event if we are bound through the DataSourceID property
                _currentView.DataSourceViewChanged += new EventHandler(OnDataSourceViewChanged); 
            }
            _currentViewValid = true;

            return _currentView; 
        }
 
        ///  
        ///  Override to create the DataSourceSelectArguments that will be passed to the view's Select command.
        ///  
        protected virtual DataSourceSelectArguments CreateDataSourceSelectArguments() {
            return DataSourceSelectArguments.Empty;
        }
 

        ///  
        /// Gets the DataSourceView of the IDataSource that this control is 
        /// bound to, if any.
        ///  
        protected virtual DataSourceView GetData() {
            DataSourceView view = ConnectToDataSourceView();

            Debug.Assert(_currentViewValid); 

            return view; 
        } 

 
        /// 
        /// Gets the IDataSource that this control is bound to, if any.
        /// Because this method can be called directly by derived classes, it's virtual so data can be retrieved
        /// from data sources that don't live on the page. 
        /// 
        protected virtual IDataSource GetDataSource() { 
            if (!DesignMode && _currentDataSourceValid && (_currentDataSource != null)) { 
                return _currentDataSource;
            } 

            IDataSource ds = null;
            string dataSourceID = DataSourceID;
 
            if (dataSourceID.Length != 0) {
                // Try to find a DataSource control with the ID specified in DataSourceID 
                Control control = DataBoundControlHelper.FindControl(this, dataSourceID); 
                if (control == null) {
                    throw new HttpException(SR.GetString(SR.DataControl_DataSourceDoesntExist, ID, dataSourceID)); 
                }
                ds = control as IDataSource;
                if (ds == null) {
                    throw new HttpException(SR.GetString(SR.DataControl_DataSourceIDMustBeDataControl, ID, dataSourceID)); 
                }
            } 
            return ds; 
        }
 
        protected void MarkAsDataBound() {
            ViewState[DataBoundViewStateKey] = true;
        }
 

        protected override void OnDataPropertyChanged() { 
            _currentViewValid = false; 
            _currentDataSourceValid = false;
            base.OnDataPropertyChanged(); 
        }


        ///  
        ///  This method is called when the DataSourceView raises a DataSourceViewChanged event.
        ///  
        protected virtual void OnDataSourceViewChanged(object sender, EventArgs e) { 
            if (!_ignoreDataSourceViewChanged) {
                RequiresDataBinding = true; 
            }
        }

        private void OnDataSourceViewSelectCallback(IEnumerable data) { 
            _ignoreDataSourceViewChanged = false;
            // We only call OnDataBinding here if we haven't done it already in PerformSelect(). 
            if (DataSourceID.Length > 0) { 
                OnDataBinding(EventArgs.Empty);
            } 

            if (AdapterInternal != null) {
                DataBoundControlAdapter dataBoundControlAdapter = AdapterInternal as DataBoundControlAdapter;
                if(dataBoundControlAdapter != null) { 
                    dataBoundControlAdapter.PerformDataBinding(data);
                } 
                else { 
                    PerformDataBinding(data);
                } 
            }
            else {
                PerformDataBinding(data);
            } 
            OnDataBound(EventArgs.Empty);
        } 
 

        protected internal override void OnLoad(EventArgs e) { 
            ConfirmInitState();
            ConnectToDataSourceView();

            if (Page != null && !_pagePreLoadFired && ViewState[DataBoundViewStateKey] == null) { 
                // If the control was added after PagePreLoad, we still need to databind it because it missed its
                // first change in PagePreLoad.  If this control was created by a call to a parent control's DataBind 
                // in Page_Load (with is relatively common), this control will already have been databound even 
                // though pagePreLoad never fired and the page isn't a postback.
                if (!Page.IsPostBack) { 
                    RequiresDataBinding = true;
                }
                // If the control was added to the page after page.PreLoad, we'll never get the event and we'll
                // never databind the control.  So if we're catching up and Load happens but PreLoad never happened, 
                // call DataBind.  This may make the control get databound twice if the user called DataBind on the control
                // directly in Page.OnLoad, but better to bind twice than never to bind at all. 
                else if (IsViewStateEnabled) { 
                    RequiresDataBinding = true;
                } 
            }

            base.OnLoad(e);
        } 

        protected override void OnPagePreLoad(object sender, EventArgs e) { 
            base.OnPagePreLoad(sender, e); 

            if (Page != null) { 
                // Setting RequiresDataBinding to true in OnLoad is too late because the OnLoad page event
                // happens before the control.OnLoad method gets called.  So a page_load handler on the page
                // that calls DataBind won't prevent DataBind from getting called again in PreRender.
                if (!Page.IsPostBack) { 
                    RequiresDataBinding = true;
                } 
                // If this is a postback and viewstate is enabled, but we have never bound the control 
                // before, it is probably because its visibility was changed in the postback.  In this
                // case, we need to bind the control or it will never appear.  This is a common scenario 
                // for Wizard and MultiView.
                else if (IsViewStateEnabled && ViewState[DataBoundViewStateKey] == null) {
                    RequiresDataBinding = true;
                } 
            }
            _pagePreLoadFired = true; 
        } 

 

        /// 
        ///  This method should be overridden by databound controls to perform their databinding.
        ///  Overriding this method instead of DataBind() will allow the DataBound control developer 
        ///  to not worry about DataBinding events to be called in the right order.
        ///  
        protected internal virtual void PerformDataBinding(IEnumerable data) { 
        }
 
        /// 
        ///  Issues an asynchronous request for data to the data source using the arguments from CreateDataSourceSelectArguments.
        /// 
        protected override void PerformSelect() { 
            // We need to call OnDataBinding here if we're potentially bound to a DataSource (instead of a DataSourceID)
            // because the databinding statement that is the datasource needs to be evaluated before the call to GetData() 
            // happens, because we don't rebind when the datasource is changed unless DataSourceID.Length > 0. 
            if (DataSourceID.Length == 0) {
                OnDataBinding(EventArgs.Empty); 
            }
            DataSourceView view = GetData();
            _arguments = CreateDataSourceSelectArguments();
            _ignoreDataSourceViewChanged = true; 
            RequiresDataBinding = false;
            MarkAsDataBound(); 
            view.Select(_arguments, OnDataSourceViewSelectCallback); 
        }
 

        protected override void ValidateDataSource(object dataSource) {
            if ((dataSource == null) ||
                (dataSource is IListSource) || 
                (dataSource is IEnumerable) ||
                (dataSource is IDataSource)) { 
                return; 
            }
            throw new InvalidOperationException(SR.GetString(SR.DataBoundControl_InvalidDataSourceType)); 
        }
    }
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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