ObjectViewFactory.cs source code in C# .NET

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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Objects / ObjectViewFactory.cs / 1599186 / ObjectViewFactory.cs

                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner       [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 
using System;
using System.Collections; 
using System.Collections.Generic;
using System.ComponentModel;
using System.Data.Common;
using System.Data.Metadata; 
using System.Data.Metadata.Edm;
using System.Data.Objects.DataClasses; 
using System.Data.Objects.Internal; 
using System.Diagnostics;
using System.Reflection; 
using System.Runtime.CompilerServices;

namespace System.Data.Objects
{ 
    /// 
    /// Creates instances of ObjectView that provide a binding list for ObjectQuery results and EntityCollections. 
    ///  
    /// 
    /// The factory methods construct an ObjectView whose generic type parameter (and typed of elements in the binding list) 
    /// is of the same type or a more specific derived type of the generic type of the ObjectQuery or EntityCollection.
    /// The EDM type of the query results or EntityType or the EntityCollection is examined to determine
    /// the appropriate type to be used.
    /// For example, if you have an ObjectQuery whose generic type is "object", but the EDM result type of the Query maps 
    /// to the CLR type "Customer", then the ObjectView returned will specify a generic type of "Customer", and not "object".
    ///  
    internal static class ObjectViewFactory 
    {
        // References to commonly-used generic type definitions. 
        private static readonly Type genericObjectViewType = typeof(ObjectView<>);

        private static readonly Type genericObjectViewDataInterfaceType = typeof(IObjectViewData<>);
        private static readonly Type genericObjectViewQueryResultDataType = typeof(ObjectViewQueryResultData<>); 
        private static readonly Type genericObjectViewEntityCollectionDataType = typeof(ObjectViewEntityCollectionData<,>);
 
        ///  
        /// Return a list suitable for data binding using the supplied query results.
        ///  
        /// 
        /// CLR type of query result elements declared by the caller.
        /// 
        ///  
        /// The EDM type of the query results, used as the primary means of determining the
        /// CLR type of list returned by this method. 
        ///  
        /// 
        /// IEnumerable used to enumerate query results used to populate binding list. 
        /// Must not be null.
        /// 
        /// 
        ///  associated with the query from which results were obtained. 
        /// Must not be null.
        ///  
        ///  
        /// True to prevent modifications to the binding list built from the query result; otherwise false.
        /// Note that other conditions may prevent the binding list from being modified, so a value of false 
        /// supplied for this parameter doesn't necessarily mean that the list will be writable.
        /// 
        /// 
        /// If the query results are composed of entities that only exist in a single , 
        /// the value of this parameter is the single EntitySet.
        /// Otherwise the value of this parameter should be null. 
        ///  
        /// 
        ///  that is suitable for data binding. 
        /// 
        [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
        internal static IBindingList CreateViewForQuery(TypeUsage elementEdmTypeUsage, IEnumerable queryResults, ObjectContext objectContext, bool forceReadOnly, EntitySet singleEntitySet)
        { 
            EntityUtil.CheckArgumentNull(queryResults, "queryResults");
            EntityUtil.CheckArgumentNull(objectContext, "objectContext"); 
 
            Type clrElementType = null;
            TypeUsage ospaceElementTypeUsage = GetOSpaceTypeUsage(elementEdmTypeUsage, objectContext); 

            // Map the O-Space EDM type to a CLR type.
            // If the mapping is unsuccessful, fallback to TElement type.
            if (ospaceElementTypeUsage == null) 
            {
                clrElementType = typeof(TElement); 
            } 
            {
                clrElementType = GetClrType(ospaceElementTypeUsage.EdmType); 
            }

            IBindingList objectView;
            object eventDataSource = objectContext.ObjectStateManager; 

            // If the clrElementType matches the declared TElement type, optimize the construction of the ObjectView 
            // by avoiding a reflection-based instantiation. 
            if (clrElementType == typeof(TElement))
            { 
                ObjectViewQueryResultData viewData = new ObjectViewQueryResultData((IEnumerable)queryResults, objectContext, forceReadOnly, singleEntitySet);

                objectView = new ObjectView(viewData, eventDataSource);
            } 
            else if (clrElementType == null)
            { 
                ObjectViewQueryResultData viewData = new ObjectViewQueryResultData((IEnumerable)queryResults, objectContext, true, null); 
                objectView = new DataRecordObjectView(viewData, eventDataSource, (RowType)ospaceElementTypeUsage.EdmType, typeof(TElement));
            } 
            else
            {
                if (!typeof(TElement).IsAssignableFrom(clrElementType))
                { 
                    throw EntityUtil.ValueInvalidCast(clrElementType, typeof(TElement));
                } 
 
                // Use reflection to create an instance of the generic ObjectView and ObjectViewQueryResultData classes,
                // using clrElementType as the value of TElement generic type parameter for both classes. 

                Type objectViewDataType = genericObjectViewQueryResultDataType.MakeGenericType(clrElementType);

                ConstructorInfo viewDataConstructor = objectViewDataType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, 
                                                                                        null,
                                                                                        new Type[] { typeof(IEnumerable), typeof(ObjectContext), typeof(bool), typeof(EntitySet) }, 
                                                                                        null); 

                Debug.Assert(viewDataConstructor != null, "ObjectViewQueryResultData constructor not found. Please ensure constructor signature is correct."); 

                // Create ObjectViewQueryResultData instance
                object viewData = viewDataConstructor.Invoke(new object[] { queryResults, objectContext, forceReadOnly, singleEntitySet });
 
                // Create ObjectView instance
                objectView = CreateObjectView(clrElementType, objectViewDataType, viewData, eventDataSource); 
            } 

            return objectView; 
        }

        /// 
        /// Return a list suitable for data binding using the supplied EntityCollection 
        /// 
        ///  
        /// CLR type of the elements of the EntityCollection. 
        /// 
        ///  
        /// The EntityType of the elements in the collection.
        /// This should either be the same as the EntityType that corresponds to the CLR TElement type,
        /// or a EntityType derived from the declared EntityCollection element type.
        ///  
        /// 
        /// The EntityCollection from which a binding list is created. 
        ///  
        /// 
        ///  that is suitable for data binding. 
        /// 
        [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
        internal static IBindingList CreateViewForEntityCollection(EntityType entityType, EntityCollection entityCollection)
            where TElement : class 
        {
            Type clrElementType = null; 
            TypeUsage entityTypeUsage = entityType == null ? null : TypeUsage.Create(entityType); 
            TypeUsage ospaceElementTypeUsage = GetOSpaceTypeUsage(entityTypeUsage, entityCollection.ObjectContext);
 
            // Map the O-Space EDM type to a CLR type.
            // If the mapping is unsuccessful, fallback to TElement type.
            if (ospaceElementTypeUsage == null)
            { 
                clrElementType = typeof(TElement);
            } 
            else 
            {
                clrElementType = GetClrType(ospaceElementTypeUsage.EdmType); 

                // A null clrElementType is returned by GetClrType if the EDM type is a RowType with no specific CLR type mapping.
                // This should not happen when working with EntityCollections, but if it does, fallback to TEntityRef type.
                Debug.Assert(clrElementType != null, "clrElementType has unexpected value of null."); 

                if (clrElementType == null) 
                { 
                    clrElementType = typeof(TElement);
                } 
            }

            IBindingList objectView;
 
            // If the clrElementType matches the declared TElement type, optimize the construction of the ObjectView
            // by avoiding a reflection-based instantiation. 
            if (clrElementType == typeof(TElement)) 
            {
                ObjectViewEntityCollectionData viewData = new ObjectViewEntityCollectionData(entityCollection); 
                objectView = new ObjectView(viewData, entityCollection);
            }
            else
            { 
                if (!typeof(TElement).IsAssignableFrom(clrElementType))
                { 
                    throw EntityUtil.ValueInvalidCast(clrElementType, typeof(TElement)); 
                }
 
                // Use reflection to create an instance of the generic ObjectView and ObjectViewEntityCollectionData classes,
                // using clrElementType as the value of TElement generic type parameter for both classes.

                Type objectViewDataType = genericObjectViewEntityCollectionDataType.MakeGenericType(clrElementType, typeof(TElement)); 

                ConstructorInfo viewDataConstructor = objectViewDataType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, 
                                                                                        null, 
                                                                                        new Type[] { typeof(EntityCollection) },
                                                                                        null); 

                Debug.Assert(viewDataConstructor != null, "ObjectViewEntityCollectionData constructor not found. Please ensure constructor signature is correct.");

                // Create ObjectViewEntityCollectionData instance 
                object viewData = viewDataConstructor.Invoke(new object[] { entityCollection });
 
                // Create ObjectView instance 
                objectView = CreateObjectView(clrElementType, objectViewDataType, viewData, entityCollection);
            } 

            return objectView;
        }
 
        /// 
        /// Create an ObjectView using reflection. 
        ///  
        /// Type to be used for the ObjectView's generic type parameter.
        /// The type of class that implements the IObjectViewData to be used by the ObjectView. 
        /// The IObjectViewData to be used by the ObjectView to access the binding list.
        /// Event source used by ObjectView for entity and membership changes.
        /// 
        [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)] 
        private static IBindingList CreateObjectView(Type clrElementType, Type objectViewDataType, object viewData, object eventDataSource)
        { 
            Type objectViewType = genericObjectViewType.MakeGenericType(clrElementType); 

            Type[] viewDataInterfaces = objectViewDataType.FindInterfaces((Type type, object unusedFilter) => type.Name == genericObjectViewDataInterfaceType.Name, null); 
            Debug.Assert(viewDataInterfaces.Length == 1, "Could not find IObjectViewData interface definition for ObjectViewQueryResultData.");

            ConstructorInfo viewConstructor = objectViewType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic,
                                                                            null, 
                                                                            new Type[] { viewDataInterfaces[0], typeof(object) },
                                                                            null); 
 
            Debug.Assert(viewConstructor != null, "ObjectView constructor not found. Please ensure constructor signature is correct.");
 
            // Create ObjectView instance
            return (IBindingList)viewConstructor.Invoke(new object[] { viewData, eventDataSource });
        }
 
        /// 
        /// Map the supplied TypeUsage to O-Space. 
        ///  
        /// 
        /// The TypeUsage to be mapped to O-Space.  Should either be associated with C-Space or O-Space. 
        /// 
        /// 
        /// ObjectContext used to perform type mapping.
        ///  
        /// 
        private static TypeUsage GetOSpaceTypeUsage(TypeUsage typeUsage, ObjectContext objectContext) 
        { 
            TypeUsage ospaceTypeUsage;
 
            if (typeUsage == null || typeUsage.EdmType == null)
            {
                ospaceTypeUsage = null;
            } 
            else
            { 
                if (typeUsage.EdmType.DataSpace == DataSpace.OSpace) 
                {
                    ospaceTypeUsage = typeUsage; 
                }
                else
                {
                    Debug.Assert(typeUsage.EdmType.DataSpace == DataSpace.CSpace, String.Format(System.Globalization.CultureInfo.InvariantCulture, "Expected EdmType.DataSpace to be C-Space, but instead it is {0}.", typeUsage.EdmType.DataSpace.ToString())); 

                    // The ObjectContext is needed to map the EDM TypeUsage from C-Space to O-Space. 
                    if (objectContext == null) 
                    {
                        ospaceTypeUsage = null; 
                    }
                    else
                    {
                        objectContext.EnsureMetadata(); 
                        ospaceTypeUsage = objectContext.Perspective.MetadataWorkspace.GetOSpaceTypeUsage(typeUsage);
                    } 
                } 
            }
 
            return ospaceTypeUsage;
        }

        ///  
        /// Determine CLR Type to be exposed for data binding using the supplied EDM item type.
        ///  
        ///  
        /// CLR element type declared by the caller.
        /// 
        /// There is no requirement that this method return the same type, or a type compatible with the declared type;
        /// it is merely a suggestion as to which type might be used.
        /// 
        ///  
        /// The EDM O-Space type of the items in a particular query result.
        ///  
        ///  
        ///  instance that represents the CLR type that corresponds to the supplied EDM item type;
        /// or null if the EDM type does not map to a CLR type. 
        /// Null is returned in the case where  is a ,
        /// and no CLR type mapping is specified in the RowType metadata.
        /// 
        private static Type GetClrType(EdmType ospaceEdmType) 
        {
            Type clrType; 
 
            // EDM RowTypes are generally represented by CLR MaterializedDataRecord types
            // that need special handling to properly expose the properties available for binding (using ICustomTypeDescriptor and ITypedList implementations, for example). 
            //
            // However, if the RowType has InitializerMetadata with a non-null CLR Type,
            // that CLR type should be used to determine the properties available for binding.
            if (ospaceEdmType.BuiltInTypeKind == BuiltInTypeKind.RowType) 
            {
                RowType itemRowType = (RowType)ospaceEdmType; 
 
                if (itemRowType.InitializerMetadata != null && itemRowType.InitializerMetadata.ClrType != null)
                { 
                    clrType = itemRowType.InitializerMetadata.ClrType;
                }
                else
                { 
                    // If the generic parameter TElement is not exactly a data record type or object type,
                    // use it as the CLR type. 
                    Type elementType = typeof(TElement); 

                    if (typeof(IDataRecord).IsAssignableFrom(elementType) || elementType == typeof(object)) 
                    {
                        // No CLR type mapping exists for this RowType.
                        clrType = null;
                    } 
                    else
                    { 
                        clrType = typeof(TElement); 
                    }
                } 
            }
            else
            {
                clrType = ospaceEdmType.ClrType; 

                // If the CLR type cannot be determined from the EDM type, 
                // fallback to the element type declared by the caller. 
                if (clrType == null)
                { 
                    clrType = typeof(TElement);
                }
            }
 
            return clrType;
        } 
    } 
}

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

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