Evaluator.cs source code in C# .NET

                        Code:
                         / Net / Net / 3.5.50727.3053 / DEVDIV / depot / DevDiv / releases / Orcas / SP / ndp / fx / src / DataWeb / Client / System / Data / Services / Client / ALinq / Evaluator.cs / 3 / 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.Linq;
    using System.Linq.Expressions; 
    using System.Diagnostics; 

#if ASTORIA_LIGHT   // Hashset not available 
    /// hack until silver light client is updated
    internal class HashSet : Dictionary, IEnumerable where T : class
    {
        /// hack until silver light client is updated 
        public HashSet() { }
 
        /// hack until silver light client is updated 
        public HashSet(IEqualityComparer comparer) : base(comparer) { }
 
        /// hack until silver light client is updated
        public bool Add(T value) { if (!base.ContainsKey(value)) { base.Add(value, value); return true; } return false; }

        /// hack until silver light client is updated 
        public bool Contains(T value) { return base.ContainsKey(value); }
 
        /// hack until silver light client is updated 
        new public bool Remove(T value) { return base.Remove(value); }
 
        /// hack until silver light client is updated
        new public IEnumerator GetEnumerator() { return base.Keys.GetEnumerator(); }
    }
#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, Func canBeEvaluated)
        { 
            return new SubtreeEvaluator(new Nominator(canBeEvaluated).Nominate(expression)).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 : DataServiceExpressionVisitor
        {
            /// list of candidates 
            private HashSet candidates;
 
            ///  
            /// constructs an expression evaluator with a list of candidates
            ///  
            /// List of expressions to evaluate
            internal SubtreeEvaluator(HashSet candidates)
            {
                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;
                }

                LambdaExpression lambda = Expression.Lambda(e); 
                Delegate fn = lambda.Compile();
                object value = fn.DynamicInvoke(null); 
                Debug.Assert(!(value is Expression), "!(value is Expression)"); 
                return Expression.Constant(value, e.Type);
            } 
        }

        /// 
        /// Performs bottom-up analysis to determine which nodes can possibly 
        /// be part of an evaluated sub-tree.
        ///  
        internal class Nominator : DataServiceExpressionVisitor 
        {
            /// func to determine whether expression can be evaluated 
            private Func functionCanBeEvaluated;

            /// candidate expressions for evaluation
            private HashSet candidates; 

            /// 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(Func functionCanBeEvaluated) 
            {
                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 HashSet Nominate(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.
//---------------------------------------------------------------------- 
// 
//      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.Linq;
    using System.Linq.Expressions; 
    using System.Diagnostics; 

#if ASTORIA_LIGHT   // Hashset not available 
    /// hack until silver light client is updated
    internal class HashSet : Dictionary, IEnumerable where T : class
    {
        /// hack until silver light client is updated 
        public HashSet() { }
 
        /// hack until silver light client is updated 
        public HashSet(IEqualityComparer comparer) : base(comparer) { }
 
        /// hack until silver light client is updated
        public bool Add(T value) { if (!base.ContainsKey(value)) { base.Add(value, value); return true; } return false; }

        /// hack until silver light client is updated 
        public bool Contains(T value) { return base.ContainsKey(value); }
 
        /// hack until silver light client is updated 
        new public bool Remove(T value) { return base.Remove(value); }
 
        /// hack until silver light client is updated
        new public IEnumerator GetEnumerator() { return base.Keys.GetEnumerator(); }
    }
#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, Func canBeEvaluated)
        { 
            return new SubtreeEvaluator(new Nominator(canBeEvaluated).Nominate(expression)).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 : DataServiceExpressionVisitor
        {
            /// list of candidates 
            private HashSet candidates;
 
            ///  
            /// constructs an expression evaluator with a list of candidates
            ///  
            /// List of expressions to evaluate
            internal SubtreeEvaluator(HashSet candidates)
            {
                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;
                }

                LambdaExpression lambda = Expression.Lambda(e); 
                Delegate fn = lambda.Compile();
                object value = fn.DynamicInvoke(null); 
                Debug.Assert(!(value is Expression), "!(value is Expression)"); 
                return Expression.Constant(value, e.Type);
            } 
        }

        /// 
        /// Performs bottom-up analysis to determine which nodes can possibly 
        /// be part of an evaluated sub-tree.
        ///  
        internal class Nominator : DataServiceExpressionVisitor 
        {
            /// func to determine whether expression can be evaluated 
            private Func functionCanBeEvaluated;

            /// candidate expressions for evaluation
            private HashSet candidates; 

            /// 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(Func functionCanBeEvaluated) 
            {
                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 HashSet Nominate(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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Evaluator.cs source code in C# .NET

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