Propagator.JoinPropagator.JoinPredicateVisitor.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 / Map / Update / Internal / Propagator.JoinPropagator.JoinPredicateVisitor.cs / 1305376 / Propagator.JoinPropagator.JoinPredicateVisitor.cs

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

using System.Data.Common.CommandTrees; 
using System.Collections.Generic;
using System.Diagnostics;
using System.Collections.ObjectModel;
namespace System.Data.Mapping.Update.Internal 
{
    internal partial class Propagator 
    { 
        private partial class JoinPropagator
        { 
            /// 
            /// Extracts equi-join properties from a join condition.
            /// 
            ///  
            /// Assumptions:
            ///  
            /// Only conjunctions of equality predicates are supported 
            /// Each equality predicate is of the form (left property == right property). The order
            /// is important. 
            /// 
            /// 
            private class JoinConditionVisitor : UpdateExpressionVisitor
            { 
                #region Constructors
                ///  
                /// Initializes a join predicate visitor. The visitor will populate the given property 
                /// lists with expressions describing the left and right hand side of equi-join
                /// sub-clauses. 
                /// 
                private JoinConditionVisitor()
                {
                    m_leftKeySelectors = new List(); 
                    m_rightKeySelectors = new List();
                } 
                #endregion 

                #region Fields 
                private readonly List m_leftKeySelectors;
                private readonly List m_rightKeySelectors;
                private static readonly string s_visitorName = typeof(JoinConditionVisitor).FullName;
                #endregion 

                #region Properties 
                override protected string VisitorName 
                {
                    get { return s_visitorName; } 
                }
                #endregion

                #region Methods 
                #region Static helper methods
                ///  
                /// Determine properties from the left and right inputs to an equi-join participating 
                /// in predicate.
                ///  
                /// 
                /// The property definitions returned are 'aligned'. If the join predicate reads:
                /// 
                /// a = b AND c = d AND e = f 
                /// 
                /// then the output is as follows: 
                ///  
                /// leftProperties = {a, c, e}
                /// rightProperties = {b, d, f} 
                /// 
                /// See Walker class for an explanation of this coding pattern.
                /// 
                static internal void GetKeySelectors(DbExpression joinCondition, out ReadOnlyCollection leftKeySelectors, out ReadOnlyCollection rightKeySelectors) 
                {
                    EntityUtil.CheckArgumentNull(joinCondition, "joinCondition"); 
 
                    // Constructs a new predicate visitor, which implements a visitor for expression nodes
                    // and returns no values. This visitor instead builds up a list of properties as leaves 
                    // of the join predicate are visited.
                    JoinConditionVisitor visitor = new JoinConditionVisitor();

                    // Walk the predicate using the predicate visitor. 
                    joinCondition.Accept(visitor);
 
                    // Retrieve properties discovered visiting predicate leaf nodes. 
                    leftKeySelectors = visitor.m_leftKeySelectors.AsReadOnly();
                    rightKeySelectors = visitor.m_rightKeySelectors.AsReadOnly(); 

                    Debug.Assert(leftKeySelectors.Count == rightKeySelectors.Count,
                        "(Update/JoinPropagator) The equi-join must have an equal number of left and right properties");
                } 
                #endregion
 
                #region Visitor implementation 
                /// 
                /// Visit and node after its children have visited. There is nothing to do here 
                /// because only leaf equality nodes contain properties extracted by this visitor.
                /// 
                /// And expression node
                /// Results ignored by this visitor implementation. 
                public override object Visit(DbAndExpression node)
                { 
                    EntityUtil.CheckArgumentNull(node, "node"); 

                    Visit(node.Left); 
                    Visit(node.Right);

                    return null;
                } 

                ///  
                /// Perform work for an equality expression node. 
                /// 
                /// Equality expresion node 
                /// Results ignored by this visitor implementation.
                public override object Visit(DbComparisonExpression node)
                {
                    EntityUtil.CheckArgumentNull(node, "node"); 

                    if (DbExpressionKind.Equals == node.ExpressionKind) 
                    { 
                        m_leftKeySelectors.Add(node.Left);
                        m_rightKeySelectors.Add(node.Right); 
                        return null;
                    }
                    else
                    { 
                        throw ConstructNotSupportedException(node);
                    } 
                } 
                #endregion
                #endregion 
            }
        }
    }
} 

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

                        

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