ObjectFullSpanRewriter.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 / DataEntity / System / Data / Objects / Internal / ObjectFullSpanRewriter.cs / 1305376 / ObjectFullSpanRewriter.cs
                        

                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner [....]
// @backupowner [....] 
//--------------------------------------------------------------------- 

using System; 
using System.Collections.Generic;
using System.Diagnostics;
using System.Data.Common;
using System.Data.Common.Utils; 
using System.Data.Metadata.Edm;
using System.Data.Common.CommandTrees; 
using System.Data.Objects.DataClasses; 
using System.Text;
using System.Data.Common.CommandTrees.ExpressionBuilder; 

namespace System.Data.Objects.Internal
{
    internal class ObjectFullSpanRewriter : ObjectSpanRewriter 
    {
        ///  
        /// Represents a node in the 'Include' navigation property tree 
        /// built from the list of SpanPaths on the Span object with which
        /// the FullSpanRewriter is constructed. 
        /// 
        private class SpanPathInfo
        {
            internal SpanPathInfo(EntityType declaringType) 
            {
                this.DeclaringType = declaringType; 
            } 

            ///  
            /// The effective Entity type of this node in the tree
            /// 
            internal EntityType DeclaringType;
 
            /// 
            /// Describes the navigation properties that should be retrieved 
            /// from this node in the tree and the Include sub-paths that extend 
            /// from each of those navigation properties
            ///  
            internal Dictionary Children;
        }

        ///  
        /// Maintains a reference to the SpanPathInfo tree node representing the
        /// current position in the 'Include' path that is currently being expanded. 
        ///  
        private Stack _currentSpanPath = new Stack();
 
        internal ObjectFullSpanRewriter(DbCommandTree tree, DbExpression toRewrite, Span span)
            : base(tree, toRewrite)
        {
            Debug.Assert(span != null, "Span cannot be null"); 
            Debug.Assert(span.SpanList.Count > 0, "At least one span path is required");
 
            // Retrieve the effective 'T' of the ObjectQuery that produced 
            // the Command Tree that is being rewritten. This could be either
            // literally 'T' or Collection. 
            EntityType entityType = null;
            if (!TryGetEntityType(this.Query.ResultType, out entityType))
            {
                // If the result type of the query is neither an Entity type nor a collection 
                // type with an Entity element type, then full Span is currently not allowed.
                throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.ObjectQuery_Span_IncludeRequiresEntityOrEntityCollection); 
            } 

            // Construct the SpanPathInfo navigation property tree using the 
            // list of Include Span paths from the Span object:
            // Create a SpanPathInfo instance that represents the root of the tree
            // and takes its Entity type from the Entity type of the result type of the query.
            SpanPathInfo spanRoot = new SpanPathInfo(entityType); 

            // Populate the tree of navigation properties based on the navigation property names 
            // in the Span paths from the Span object. Commonly rooted span paths are merged, so 
            // that paths of "Customer.Order" and "Customer.Address", for example, will share a
            // common SpanPathInfo for "Customer" in the Children collection of the root SpanPathInfo, 
            // and that SpanPathInfo will contain one child for "Order" and another for "Address".
            foreach (Span.SpanPath path in span.SpanList)
            {
                AddSpanPath(spanRoot, path.Navigations); 
            }
 
            // The 'current' span path is initialized to the root of the Include span tree 
            _currentSpanPath.Push(spanRoot);
        } 

        /// 
        /// Populates the Include span tree with appropriate branches for the Include path
        /// represented by the specified list of navigation property names. 
        /// 
        /// The root SpanPathInfo 
        /// A list of navigation property names that describes a single Include span path 
        private void AddSpanPath(SpanPathInfo parentInfo, List navPropNames)
        { 
            ConvertSpanPath(parentInfo, navPropNames, 0);
        }

        private void ConvertSpanPath(SpanPathInfo parentInfo, List navPropNames, int pos) 
        {
            // Attempt to retrieve the next navigation property from the current entity type 
            // using the name of the current navigation property in the Include path. 
            NavigationProperty nextNavProp = null;
            if (!parentInfo.DeclaringType.NavigationProperties.TryGetValue(navPropNames[pos], true, out nextNavProp)) 
            {
                // The navigation property name is not valid for this Entity type
                throw EntityUtil.InvalidOperation(System.Data.Entity.Strings.ObjectQuery_Span_NoNavProp(parentInfo.DeclaringType.FullName, navPropNames[pos]));
            } 

            // The navigation property was retrieved, an entry for it must be ensured in the Children 
            // collection of the parent SpanPathInfo instance. 
            // If the parent's Children collection does not exist then instantiate it now:
            if (null == parentInfo.Children) 
            {
                parentInfo.Children = new Dictionary();
            }
 
            // If a sub-path that begins with the current navigation property name was already
            // encountered, then a SpanPathInfo for this navigation property may already exist 
            // in the Children dictionary... 
            SpanPathInfo nextChild = null;
            if (!parentInfo.Children.TryGetValue(nextNavProp, out nextChild)) 
            {
                // ... otherwise, create a new SpanPathInfo instance that this navigation
                // property maps to and ensure its presence in the Children dictionary.
                nextChild = new SpanPathInfo(EntityTypeFromResultType(nextNavProp)); 
                parentInfo.Children[nextNavProp] = nextChild;
            } 
 
            // If this navigation property is not the end of the span path then
            // increment the position and recursively call ConvertSpanPath, specifying 
            // the (retrieved or newly-created) SpanPathInfo of this navigation property
            // as the new 'parent' info.
            if (pos < navPropNames.Count - 1)
            { 
                ConvertSpanPath(nextChild, navPropNames, pos + 1);
            } 
        } 

        ///  
        /// Retrieves the Entity (result or element) type produced by a Navigation Property.
        /// 
        /// The navigation property
        ///  
        ///     The Entity type produced by the navigation property.
        ///     This may be the immediate result type (if the result is at most one) 
        ///     or the element type of the result type, otherwise. 
        /// 
        private static EntityType EntityTypeFromResultType(NavigationProperty navProp) 
        {
            EntityType retType = null;
            TryGetEntityType(navProp.TypeUsage, out retType);
            // Currently, navigation properties may only return an Entity or Collection result 
            Debug.Assert(retType != null, "Navigation property has non-Entity and non-Entity collection result type?");
            return retType; 
        } 

        ///  
        /// Retrieves the Entity (result or element) type referenced by the specified TypeUsage, if
        /// its EdmType is an Entity type or a collection type with an Entity element type.
        /// 
        /// The TypeUsage that provides the EdmType to examine 
        /// The referenced Entity (element) type, if present.
        ///  
        ///     true if the specified  is an Entity type or a 
        ///     collection type with an Entity element type; otherwise false.
        ///  
        private static bool TryGetEntityType(TypeUsage resultType, out EntityType entityType)
        {
            // If the result type is an Entity, then simply use that type.
            if (BuiltInTypeKind.EntityType == resultType.EdmType.BuiltInTypeKind) 
            {
                entityType = (EntityType)resultType.EdmType; 
                return true; 
            }
            else if (BuiltInTypeKind.CollectionType == resultType.EdmType.BuiltInTypeKind) 
            {
                // If the result type of the query is a collection, attempt to extract
                // the element type of the collection and determine if it is an Entity type.
                EdmType elementType = ((CollectionType)resultType.EdmType).TypeUsage.EdmType; 
                if (BuiltInTypeKind.EntityType == elementType.BuiltInTypeKind)
                { 
                    entityType = (EntityType)elementType; 
                    return true;
                } 
            }

            entityType = null;
            return false; 
        }
 
        ///  
        /// Utility method to retrieve the 'To' AssociationEndMember of a NavigationProperty
        ///  
        /// The navigation property
        /// The AssociationEndMember that is the target of the navigation operation represented by the NavigationProperty
        private AssociationEndMember GetNavigationPropertyTargetEnd(NavigationProperty property)
        { 
            AssociationType relationship = this.Metadata.GetItem(property.RelationshipType.FullName, DataSpace.CSpace);
            Debug.Assert(relationship.AssociationEndMembers.Contains(property.ToEndMember.Name), "Association does not declare member referenced by Navigation property?"); 
            return relationship.AssociationEndMembers[property.ToEndMember.Name]; 
        }
 
        internal override SpanTrackingInfo CreateEntitySpanTrackingInfo(DbExpression expression, EntityType entityType)
        {
            SpanTrackingInfo tracking = new SpanTrackingInfo();
 
            SpanPathInfo currentInfo = _currentSpanPath.Peek();
            if (currentInfo.Children != null) 
            { 
                // The current SpanPathInfo instance on the top of the span path stack indicates
                // which navigation properties should be retrieved from this Entity-typed expression 
                // and also specifies (in the form of child SpanPathInfo instances) which sub-paths
                // must be expanded for each of those navigation properties.
                // The SpanPathInfo instance may be the root instance or a SpanPathInfo that represents a sub-path.
                int idx = 1; // SpanRoot is always the first (zeroth) column, full- and relationship-span columns follow. 
                foreach (KeyValuePair nextInfo in currentInfo.Children)
                { 
                    // If the tracking information was not initialized yet, do so now. 
                    if (null == tracking.ColumnDefinitions)
                    { 
                        tracking = InitializeTrackingInfo(this.RelationshipSpan);
                    }

                    // Create a property expression that retrieves the specified navigation property from the Entity-typed expression. 
                    // Note that the expression is cloned since it may be used as the instance of multiple property expressions.
                    DbExpression columnDef = expression.Property(nextInfo.Key); 
 
                    // Rewrite the result of the navigation property. This is required for two reasons:
                    // 1. To continue spanning the current Include path. 
                    // 2. To apply relationship span to the Entity or EntityCollection produced by the navigation property, if necessary.
                    //    Consider an Include path of "Order" for a query that returns OrderLines - the Include'd Orders should have
                    //    their associated Customer relationship spanned.
                    // Note that this will recursively call this method with the Entity type of the result of the 
                    // navigation property, which will in turn call loop through the sub-paths of this navigation
                    // property and adjust the stack to track which Include path is being expanded and which 
                    // element of that path is considered 'current'. 
                    _currentSpanPath.Push(nextInfo.Value);
                    columnDef = this.Rewrite(columnDef); 
                    _currentSpanPath.Pop();

                    // Add a new column to the tracked columns using the rewritten column definition
                    tracking.ColumnDefinitions.Add(new KeyValuePair(tracking.ColumnNames.Next(), columnDef)); 
                    AssociationEndMember targetEnd = GetNavigationPropertyTargetEnd(nextInfo.Key);
                    tracking.SpannedColumns[idx] = targetEnd; 
 
                    // If full span and relationship span are both required, a relationship span may be rendered
                    // redundant by an already added full span. Therefore the association ends that have been expanded 
                    // as part of full span are tracked using a dictionary.
                    if (this.RelationshipSpan)
                    {
                        tracking.FullSpannedEnds[targetEnd] = true; 
                    }
 
                    idx++; 
                }
            } 

            return tracking;
        }
    } 
}

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

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