ProjectionRewriter.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 / DataWeb / Client / System / Data / Services / Client / ALinq / ProjectionRewriter.cs / 1305376 / ProjectionRewriter.cs

                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//  
//      Tries to remove transparent identifiers from selector expressions
//      so it can be used as a projection. 
//  
//
// @owner  [....] 
//---------------------------------------------------------------------

namespace System.Data.Services.Client
{ 
    #region Namespaces.
 
    using System; 
    using System.Diagnostics;
    using System.Linq; 
    using System.Linq.Expressions;

    #endregion Namespaces.
 
    internal class ProjectionRewriter : ALinqExpressionVisitor
    { 
        #region Private fields. 

        private readonly ParameterExpression newLambdaParameter; 

        private ParameterExpression oldLambdaParameter;

        private bool sucessfulRebind; 

        #endregion Private fields. 
 
        private ProjectionRewriter(Type proposedParameterType)
        { 
            Debug.Assert(proposedParameterType != null, "proposedParameterType != null");
            this.newLambdaParameter = Expression.Parameter(proposedParameterType, "it");
        }
 
        #region Internal methods.
 
        internal static LambdaExpression TryToRewrite(LambdaExpression le, Type proposedParameterType) 
        {
            LambdaExpression result; 
            if (!ResourceBinder.PatternRules.MatchSingleArgumentLambda(le, out le) ||  // can only rewrite single parameter Lambdas.
                ClientType.CheckElementTypeIsEntity(le.Parameters[0].Type) || // only attempt to rewrite if lambda parameter is not an entity type
                !(le.Parameters[0].Type.GetProperties().Any(p => p.PropertyType == proposedParameterType))) // lambda parameter must have public property that is same as proposed type.
            { 
                result = le;
            } 
            else 
            {
                ProjectionRewriter rewriter = new ProjectionRewriter(proposedParameterType); 
                result = rewriter.Rebind(le);
            }

            return result; 
        }
 
        internal LambdaExpression Rebind(LambdaExpression lambda) 
        {
            this.sucessfulRebind = true; 
            this.oldLambdaParameter = lambda.Parameters[0];

            Expression body = this.Visit(lambda.Body);
            if (this.sucessfulRebind) 
            {
                Type delegateType = typeof(Func<,>).MakeGenericType(new Type[] { newLambdaParameter.Type, lambda.Body.Type }); 
#if ASTORIA_LIGHT 
                return ExpressionHelpers.CreateLambda(delegateType, body, new ParameterExpression[] { this.newLambdaParameter });
#else 
                return Expression.Lambda(delegateType, body, new ParameterExpression[] { this.newLambdaParameter });
#endif
            }
            else 
            {
                throw new NotSupportedException(Strings.ALinq_CanOnlyProjectTheLeaf); 
            } 
        }
 
        internal override Expression VisitMemberAccess(MemberExpression m)
        {
            if (m.Expression == this.oldLambdaParameter)
            { 
                if (m.Type == this.newLambdaParameter.Type)
                { 
                    return this.newLambdaParameter; 
                }
                else 
                {
                    this.sucessfulRebind = false;
                }
            } 

            return base.VisitMemberAccess(m); 
        } 

        #endregion Internal methods. 
    }
}

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

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