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//---------------------------------------------------------------------
// <copyright file="ObjectViewFactory.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
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
{
/// <summary>
/// Creates instances of ObjectView that provide a binding list for ObjectQuery results and EntityCollections.
/// </summary>
/// <remarks>
/// 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".
/// </remarks>
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<,>);
/// <summary>
/// Return a list suitable for data binding using the supplied query results.
/// </summary>
/// <typeparam name="TElement">
/// CLR type of query result elements declared by the caller.
/// </typeparam>
/// <param name="elementEdmTypeUsage">
/// The EDM type of the query results, used as the primary means of determining the
/// CLR type of list returned by this method.
/// </param>
/// <param name="queryResults">
/// IEnumerable used to enumerate query results used to populate binding list.
/// Must not be null.
/// </param>
/// <param name="objectContext">
/// <see cref="ObjectContext"/> associated with the query from which results were obtained.
/// Must not be null.
/// </param>
/// <param name="forceReadOnly">
/// <b>True</b> to prevent modifications to the binding list built from the query result; otherwise <b>false</b>.
/// Note that other conditions may prevent the binding list from being modified, so a value of <b>false</b>
/// supplied for this parameter doesn't necessarily mean that the list will be writable.
/// </param>
/// <param name="singleEntitySet">
/// If the query results are composed of entities that only exist in a single <see cref="EntitySet"/>,
/// the value of this parameter is the single EntitySet.
/// Otherwise the value of this parameter should be null.
/// </param>
/// <returns>
/// <see cref="IBindingList"/> that is suitable for data binding.
/// </returns>
[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
internal static IBindingList CreateViewForQuery<TElement>(TypeUsage elementEdmTypeUsage, IEnumerable<TElement> 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<TElement>(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<TElement> viewData = new ObjectViewQueryResultData<TElement>((IEnumerable)queryResults, objectContext, forceReadOnly, singleEntitySet);
objectView = new ObjectView<TElement>(viewData, eventDataSource);
}
else if (clrElementType == null)
{
ObjectViewQueryResultData<DbDataRecord> viewData = new ObjectViewQueryResultData<DbDataRecord>((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;
}
/// <summary>
/// Return a list suitable for data binding using the supplied EntityCollection
/// </summary>
/// <typeparam name="TElement">
/// CLR type of the elements of the EntityCollection.
/// </typeparam>
/// <param name="entityType">
/// 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.
/// </param>
/// <param name="entityCollection">
/// The EntityCollection from which a binding list is created.
/// </param>
/// <returns>
/// <see cref="IBindingList"/> that is suitable for data binding.
/// </returns>
[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
internal static IBindingList CreateViewForEntityCollection<TElement>(EntityType entityType, EntityCollection<TElement> 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<TElement>(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<TElement, TElement> viewData = new ObjectViewEntityCollectionData<TElement, TElement>(entityCollection);
objectView = new ObjectView<TElement>(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<TElement>) },
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;
}
/// <summary>
/// Create an ObjectView using reflection.
/// </summary>
/// <param name="clrElementType">Type to be used for the ObjectView's generic type parameter.</param>
/// <param name="objectViewDataType">The type of class that implements the IObjectViewData to be used by the ObjectView.</param>
/// <param name="viewData">The IObjectViewData to be used by the ObjectView to access the binding list.</param>
/// <param name="eventDataSource">Event source used by ObjectView for entity and membership changes.</param>
/// <returns></returns>
[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<T> interface definition for ObjectViewQueryResultData<T>.");
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 });
}
/// <summary>
/// Map the supplied TypeUsage to O-Space.
/// </summary>
/// <param name="typeUsage">
/// The TypeUsage to be mapped to O-Space. Should either be associated with C-Space or O-Space.
/// </param>
/// <param name="objectContext">
/// ObjectContext used to perform type mapping.
/// </param>
/// <returns></returns>
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;
}
/// <summary>
/// Determine CLR Type to be exposed for data binding using the supplied EDM item type.
/// </summary>
/// <typeparam name="TElement">
/// 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.
/// </typeparam>
/// <param name="ospaceEdmType">
/// The EDM O-Space type of the items in a particular query result.
/// </param>
/// <returns>
/// <see cref="Type"/> 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 <paramref name="ospaceEdmType"/> is a <see cref="RowType"/>,
/// and no CLR type mapping is specified in the RowType metadata.
/// </returns>
private static Type GetClrType<TElement>(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;
}
}
}
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