264 lines
14 KiB
C#
264 lines
14 KiB
C#
//---------------------------------------------------------------------
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// <copyright file="ObjectFullSpanRewriter.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//
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// @owner Microsoft
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// @backupowner Microsoft
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//---------------------------------------------------------------------
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namespace System.Data.Objects.Internal
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{
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using System.Collections.Generic;
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using System.Data.Common.CommandTrees;
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using System.Data.Common.CommandTrees.ExpressionBuilder;
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using System.Data.Common.Utils;
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using System.Data.Metadata.Edm;
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using System.Diagnostics;
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internal class ObjectFullSpanRewriter : ObjectSpanRewriter
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{
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/// <summary>
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/// Represents a node in the 'Include' navigation property tree
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/// built from the list of SpanPaths on the Span object with which
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/// the FullSpanRewriter is constructed.
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/// </summary>
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private class SpanPathInfo
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{
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internal SpanPathInfo(EntityType declaringType)
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{
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this.DeclaringType = declaringType;
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}
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/// <summary>
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/// The effective Entity type of this node in the tree
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/// </summary>
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internal EntityType DeclaringType;
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/// <summary>
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/// Describes the navigation properties that should be retrieved
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/// from this node in the tree and the Include sub-paths that extend
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/// from each of those navigation properties
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/// </summary>
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internal Dictionary<NavigationProperty, SpanPathInfo> Children;
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}
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/// <summary>
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/// Maintains a reference to the SpanPathInfo tree node representing the
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/// current position in the 'Include' path that is currently being expanded.
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/// </summary>
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private Stack<SpanPathInfo> _currentSpanPath = new Stack<SpanPathInfo>();
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internal ObjectFullSpanRewriter(DbCommandTree tree, DbExpression toRewrite, Span span, AliasGenerator aliasGenerator)
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: base(tree, toRewrite, aliasGenerator)
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{
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Debug.Assert(span != null, "Span cannot be null");
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Debug.Assert(span.SpanList.Count > 0, "At least one span path is required");
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// Retrieve the effective 'T' of the ObjectQuery<T> that produced
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// the Command Tree that is being rewritten. This could be either
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// literally 'T' or Collection<T>.
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EntityType entityType = null;
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if (!TryGetEntityType(this.Query.ResultType, out entityType))
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{
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// If the result type of the query is neither an Entity type nor a collection
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// type with an Entity element type, then full Span is currently not allowed.
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throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.ObjectQuery_Span_IncludeRequiresEntityOrEntityCollection);
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}
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// Construct the SpanPathInfo navigation property tree using the
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// list of Include Span paths from the Span object:
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// Create a SpanPathInfo instance that represents the root of the tree
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// and takes its Entity type from the Entity type of the result type of the query.
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SpanPathInfo spanRoot = new SpanPathInfo(entityType);
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// Populate the tree of navigation properties based on the navigation property names
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// in the Span paths from the Span object. Commonly rooted span paths are merged, so
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// that paths of "Customer.Order" and "Customer.Address", for example, will share a
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// common SpanPathInfo for "Customer" in the Children collection of the root SpanPathInfo,
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// and that SpanPathInfo will contain one child for "Order" and another for "Address".
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foreach (Span.SpanPath path in span.SpanList)
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{
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AddSpanPath(spanRoot, path.Navigations);
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}
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// The 'current' span path is initialized to the root of the Include span tree
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_currentSpanPath.Push(spanRoot);
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}
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/// <summary>
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/// Populates the Include span tree with appropriate branches for the Include path
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/// represented by the specified list of navigation property names.
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/// </summary>
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/// <param name="parentInfo">The root SpanPathInfo</param>
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/// <param name="navPropNames">A list of navigation property names that describes a single Include span path</param>
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private void AddSpanPath(SpanPathInfo parentInfo, List<string> navPropNames)
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{
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ConvertSpanPath(parentInfo, navPropNames, 0);
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}
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private void ConvertSpanPath(SpanPathInfo parentInfo, List<string> navPropNames, int pos)
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{
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// Attempt to retrieve the next navigation property from the current entity type
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// using the name of the current navigation property in the Include path.
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NavigationProperty nextNavProp = null;
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if (!parentInfo.DeclaringType.NavigationProperties.TryGetValue(navPropNames[pos], true, out nextNavProp))
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{
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// The navigation property name is not valid for this Entity type
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throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.ObjectQuery_Span_NoNavProp(parentInfo.DeclaringType.FullName, navPropNames[pos]));
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}
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// The navigation property was retrieved, an entry for it must be ensured in the Children
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// collection of the parent SpanPathInfo instance.
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// If the parent's Children collection does not exist then instantiate it now:
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if (null == parentInfo.Children)
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{
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parentInfo.Children = new Dictionary<NavigationProperty, SpanPathInfo>();
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}
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// If a sub-path that begins with the current navigation property name was already
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// encountered, then a SpanPathInfo for this navigation property may already exist
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// in the Children dictionary...
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SpanPathInfo nextChild = null;
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if (!parentInfo.Children.TryGetValue(nextNavProp, out nextChild))
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{
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// ... otherwise, create a new SpanPathInfo instance that this navigation
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// property maps to and ensure its presence in the Children dictionary.
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nextChild = new SpanPathInfo(EntityTypeFromResultType(nextNavProp));
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parentInfo.Children[nextNavProp] = nextChild;
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}
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// If this navigation property is not the end of the span path then
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// increment the position and recursively call ConvertSpanPath, specifying
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// the (retrieved or newly-created) SpanPathInfo of this navigation property
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// as the new 'parent' info.
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if (pos < navPropNames.Count - 1)
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{
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ConvertSpanPath(nextChild, navPropNames, pos + 1);
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}
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}
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/// <summary>
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/// Retrieves the Entity (result or element) type produced by a Navigation Property.
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/// </summary>
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/// <param name="navProp">The navigation property</param>
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/// <returns>
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/// The Entity type produced by the navigation property.
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/// This may be the immediate result type (if the result is at most one)
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/// or the element type of the result type, otherwise.
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/// </returns>
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private static EntityType EntityTypeFromResultType(NavigationProperty navProp)
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{
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EntityType retType = null;
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TryGetEntityType(navProp.TypeUsage, out retType);
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// Currently, navigation properties may only return an Entity or Collection<Entity> result
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Debug.Assert(retType != null, "Navigation property has non-Entity and non-Entity collection result type?");
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return retType;
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}
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/// <summary>
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/// Retrieves the Entity (result or element) type referenced by the specified TypeUsage, if
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/// its EdmType is an Entity type or a collection type with an Entity element type.
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/// </summary>
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/// <param name="resultType">The TypeUsage that provides the EdmType to examine</param>
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/// <param name="entityType">The referenced Entity (element) type, if present.</param>
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/// <returns>
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/// <c>true</c> if the specified <paramref name="resultType"/> is an Entity type or a
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/// collection type with an Entity element type; otherwise <c>false</c>.
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/// </returns>
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private static bool TryGetEntityType(TypeUsage resultType, out EntityType entityType)
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{
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// If the result type is an Entity, then simply use that type.
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if (BuiltInTypeKind.EntityType == resultType.EdmType.BuiltInTypeKind)
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{
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entityType = (EntityType)resultType.EdmType;
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return true;
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}
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else if (BuiltInTypeKind.CollectionType == resultType.EdmType.BuiltInTypeKind)
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{
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// If the result type of the query is a collection, attempt to extract
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// the element type of the collection and determine if it is an Entity type.
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EdmType elementType = ((CollectionType)resultType.EdmType).TypeUsage.EdmType;
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if (BuiltInTypeKind.EntityType == elementType.BuiltInTypeKind)
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{
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entityType = (EntityType)elementType;
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return true;
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}
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}
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entityType = null;
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return false;
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}
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/// <summary>
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/// Utility method to retrieve the 'To' AssociationEndMember of a NavigationProperty
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/// </summary>
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/// <param name="property">The navigation property</param>
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/// <returns>The AssociationEndMember that is the target of the navigation operation represented by the NavigationProperty</returns>
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private AssociationEndMember GetNavigationPropertyTargetEnd(NavigationProperty property)
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{
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AssociationType relationship = this.Metadata.GetItem<AssociationType>(property.RelationshipType.FullName, DataSpace.CSpace);
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Debug.Assert(relationship.AssociationEndMembers.Contains(property.ToEndMember.Name), "Association does not declare member referenced by Navigation property?");
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return relationship.AssociationEndMembers[property.ToEndMember.Name];
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}
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internal override SpanTrackingInfo CreateEntitySpanTrackingInfo(DbExpression expression, EntityType entityType)
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{
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SpanTrackingInfo tracking = new SpanTrackingInfo();
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SpanPathInfo currentInfo = _currentSpanPath.Peek();
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if (currentInfo.Children != null)
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{
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// The current SpanPathInfo instance on the top of the span path stack indicates
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// which navigation properties should be retrieved from this Entity-typed expression
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// and also specifies (in the form of child SpanPathInfo instances) which sub-paths
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// must be expanded for each of those navigation properties.
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// The SpanPathInfo instance may be the root instance or a SpanPathInfo that represents a sub-path.
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int idx = 1; // SpanRoot is always the first (zeroth) column, full- and relationship-span columns follow.
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foreach (KeyValuePair<NavigationProperty, SpanPathInfo> nextInfo in currentInfo.Children)
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{
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// If the tracking information was not initialized yet, do so now.
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if (null == tracking.ColumnDefinitions)
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{
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tracking = InitializeTrackingInfo(this.RelationshipSpan);
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}
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// Create a property expression that retrieves the specified navigation property from the Entity-typed expression.
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// Note that the expression is cloned since it may be used as the instance of multiple property expressions.
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DbExpression columnDef = expression.Property(nextInfo.Key);
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// Rewrite the result of the navigation property. This is required for two reasons:
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// 1. To continue spanning the current Include path.
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// 2. To apply relationship span to the Entity or EntityCollection produced by the navigation property, if necessary.
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// Consider an Include path of "Order" for a query that returns OrderLines - the Include'd Orders should have
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// their associated Customer relationship spanned.
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// Note that this will recursively call this method with the Entity type of the result of the
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// navigation property, which will in turn call loop through the sub-paths of this navigation
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// property and adjust the stack to track which Include path is being expanded and which
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// element of that path is considered 'current'.
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_currentSpanPath.Push(nextInfo.Value);
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columnDef = this.Rewrite(columnDef);
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_currentSpanPath.Pop();
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// Add a new column to the tracked columns using the rewritten column definition
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tracking.ColumnDefinitions.Add(new KeyValuePair<string, DbExpression>(tracking.ColumnNames.Next(), columnDef));
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AssociationEndMember targetEnd = GetNavigationPropertyTargetEnd(nextInfo.Key);
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tracking.SpannedColumns[idx] = targetEnd;
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// If full span and relationship span are both required, a relationship span may be rendered
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// redundant by an already added full span. Therefore the association ends that have been expanded
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// as part of full span are tracked using a dictionary.
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if (this.RelationshipSpan)
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{
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tracking.FullSpannedEnds[targetEnd] = true;
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}
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idx++;
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}
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}
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return tracking;
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}
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}
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}
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