Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataWeb / Client / System / Data / Services / Client / ALinq / Evaluator.cs / 1305376 / Evaluator.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // //// Provides funcletization of expression tree prior to resource binding. // // // @owner [....] //--------------------------------------------------------------------- namespace System.Data.Services.Client { using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq.Expressions; #if ASTORIA_LIGHT // Hashset not available ///workaround until silver light client is updated internal class HashSet: Dictionary , IEnumerable where T : class { /// workaround until silver light client is updated public HashSet() { } ///workaround until silver light client is updated public HashSet(IEqualityComparercomparer) : base(comparer) { } /// workaround until silver light client is updated public HashSet(IEnumerablecollection, IEqualityComparer comparer) : base(comparer) { this.UnionWith(collection); } /// workaround until silver light client is updated public bool Add(T value) { if (!base.ContainsKey(value)) { base.Add(value, value); return true; } return false; } ///workaround until silver light client is updated public bool Contains(T value) { return base.ContainsKey(value); } ///workaround until silver light client is updated new public bool Remove(T value) { return base.Remove(value); } ///workaround until silver light client is updated new public IEnumeratorGetEnumerator() { return base.Keys.GetEnumerator(); } /// Modifies the current HashSet object to contain all elements that are present in both itself and in the specified collection. /// The collection to compare to the current HashSet object. public void UnionWith(IEnumerableother) { if (other == null) { throw new ArgumentNullException("other"); } foreach (T local in other) { ////this.AddIfNotPresent(local); this.Add(local); } } } #endif /// /// performs funcletization on an expression tree /// internal static class Evaluator { ////// Performs evaluation and replacement of independent sub-trees /// /// The root of the expression tree. /// A function that decides whether a given expression node can be part of the local function. ///A new tree with sub-trees evaluated and replaced. internal static Expression PartialEval(Expression expression, FunccanBeEvaluated) { Nominator nominator = new Nominator(canBeEvaluated); HashSet candidates = nominator.Nominate(expression); return new SubtreeEvaluator(candidates).Eval(expression); } /// /// Performs evaluation and replacement of independent sub-trees /// /// The root of the expression tree. ///A new tree with sub-trees evaluated and replaced. internal static Expression PartialEval(Expression expression) { return PartialEval(expression, Evaluator.CanBeEvaluatedLocally); } ////// Evaluates if an expression can be evaluated locally. /// /// the expression. ///true/ false if can be evaluated locally private static bool CanBeEvaluatedLocally(Expression expression) { return expression.NodeType != ExpressionType.Parameter && expression.NodeType != ExpressionType.Lambda && expression.NodeType != (ExpressionType) ResourceExpressionType.RootResourceSet; } ////// Evaluates and replaces sub-trees when first candidate is reached (top-down) /// internal class SubtreeEvaluator : DataServiceALinqExpressionVisitor { ///list of candidates private HashSetcandidates; /// /// constructs an expression evaluator with a list of candidates /// /// List of expressions to evaluate internal SubtreeEvaluator(HashSetcandidates) { this.candidates = candidates; } /// /// Evaluates an expression sub-tree /// /// The expression to evaluate. ///The evaluated expression. internal Expression Eval(Expression exp) { return this.Visit(exp); } ////// Visit method for visitor /// /// the expression to visit ///visited expression internal override Expression Visit(Expression exp) { if (exp == null) { return null; } if (this.candidates.Contains(exp)) { return Evaluate(exp); } return base.Visit(exp); } ////// Evaluates expression /// /// the expression to evaluate ///constant expression with return value of evaluation private static Expression Evaluate(Expression e) { if (e.NodeType == ExpressionType.Constant) { return e; } #if ASTORIA_LIGHT LambdaExpression lambda = ExpressionHelpers.CreateLambda(e, new ParameterExpression[0]); #else LambdaExpression lambda = Expression.Lambda(e); #endif Delegate fn = lambda.Compile(); object constantValue = fn.DynamicInvoke(null); Debug.Assert(!(constantValue is Expression), "!(constantValue is Expression)"); // Use the expression type unless it's an array type, // where the actual type may be a vector array rather // than an array with a dynamic lower bound. Type constantType = e.Type; if (constantValue != null && constantType.IsArray && constantType.GetElementType() == constantValue.GetType().GetElementType()) { constantType = constantValue.GetType(); } return Expression.Constant(constantValue, constantType); } } ////// Performs bottom-up analysis to determine which nodes can possibly /// be part of an evaluated sub-tree. /// internal class Nominator : DataServiceALinqExpressionVisitor { ///func to determine whether expression can be evaluated private FuncfunctionCanBeEvaluated; /// candidate expressions for evaluation private HashSetcandidates; /// flag for when sub tree cannot be evaluated private bool cannotBeEvaluated; ////// Creates the Nominator based on the function passed. /// /// /// A Func speficying whether an expression can be evaluated or not. /// ///visited expression internal Nominator(FuncfunctionCanBeEvaluated) { this.functionCanBeEvaluated = functionCanBeEvaluated; } /// /// Nominates an expression to see if it can be evaluated /// /// /// Expression to check /// ///a list of expression sub trees that can be evaluated internal HashSetNominate(Expression expression) { this.candidates = new HashSet (EqualityComparer .Default); this.Visit(expression); return this.candidates; } /// /// Visit method for walking expression tree bottom up. /// /// /// root expression to visit /// ///visited expression internal override Expression Visit(Expression expression) { if (expression != null) { bool saveCannotBeEvaluated = this.cannotBeEvaluated; this.cannotBeEvaluated = false; base.Visit(expression); if (!this.cannotBeEvaluated) { if (this.functionCanBeEvaluated(expression)) { this.candidates.Add(expression); } else { this.cannotBeEvaluated = true; } } this.cannotBeEvaluated |= saveCannotBeEvaluated; } return expression; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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