1 /* ****************************************************************************
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3 * Copyright (c) Microsoft Corporation. All rights reserved.
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5 * This software is subject to the Microsoft Public License (Ms-PL).
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6 * A copy of the license can be found in the license.htm file included
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7 * in this distribution.
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9 * You must not remove this notice, or any other, from this software.
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11 * ***************************************************************************/
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13 namespace System.Web.Mvc.ExpressionUtil {
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15 using System.Linq.Expressions;
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16 using System.Reflection;
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18 internal static class FastTrack<TModel, TValue> {
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20 private static Func<TModel, TValue> _identityFunc;
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22 private static readonly ConstMemberLookupCache _constMemberLookupCache = new ConstMemberLookupCache();
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23 private static readonly ModelMemberLookupCache _modelMemberLookupCache = new ModelMemberLookupCache();
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25 public static Func<TModel, TValue> GetFunc(ParameterExpression modelParameter, Expression body) {
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27 if (modelParameter == body) {
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28 return GetIdentityFunc();
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32 { // model => {const}
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33 ConstantExpression constantExpression = body as ConstantExpression;
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34 if (constantExpression != null) {
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35 TValue value = (TValue)constantExpression.Value;
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41 MemberExpression memberExpression = body as MemberExpression;
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42 if (memberExpression != null) {
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43 if (memberExpression.Expression == null) {
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44 // model => {static member}
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45 return GetModelMemberLookupFunc(memberExpression.Member, true /* isStatic */);
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47 else if (memberExpression.Expression == modelParameter) {
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48 // model => model.Member
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49 return GetModelMemberLookupFunc(memberExpression.Member, false /* isStatic */);
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52 ConstantExpression constantExpression = memberExpression.Expression as ConstantExpression;
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53 if (constantExpression != null) {
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54 // model => {const}.Member, e.g. captured local variable in a foreach
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55 return GetConstMemberLookupFunc(memberExpression.Member, constantExpression.Value);
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61 // don't know how to fast-track
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65 private static Func<TModel, TValue> GetIdentityFunc() {
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66 // don't need to worry about locking since all identity funcs are the same
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67 if (_identityFunc == null) {
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68 ParameterExpression modelParameter = Expression.Parameter(typeof(TModel), "model");
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69 Expression<Func<TModel, TValue>> identityLambda = Expression.Lambda<Func<TModel, TValue>>(modelParameter, modelParameter);
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70 _identityFunc = identityLambda.Compile();
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73 return _identityFunc;
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76 private static Func<TModel, TValue> GetModelMemberLookupFunc(MemberInfo member, bool isStatic) {
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77 return _modelMemberLookupCache.GetFunc(member, isStatic);
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80 private static Func<TModel, TValue> GetConstMemberLookupFunc(MemberInfo member, object constValue) {
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81 Func<object, TValue> innerFunc = _constMemberLookupCache.GetFunc(member);
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82 return _ => innerFunc(constValue);
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85 private sealed class ConstMemberLookupCache : ReaderWriterCache<MemberInfo, Func<object, TValue>> {
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86 private static Func<object, TValue> CreateFunc(MemberInfo member) {
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87 ParameterExpression constParam = Expression.Parameter(typeof(object), "constValue");
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88 // cast is necessary since the constant value comes in as a standard 'object'
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89 UnaryExpression castExpr = Expression.Convert(constParam, member.DeclaringType);
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90 MemberExpression memberExpr = Expression.MakeMemberAccess(castExpr, member);
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91 Expression<Func<object, TValue>> lambda = Expression.Lambda<Func<object, TValue>>(memberExpr, constParam);
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92 return lambda.Compile();
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94 public Func<object, TValue> GetFunc(MemberInfo member) {
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95 return FetchOrCreateItem(member, () => CreateFunc(member));
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99 private sealed class ModelMemberLookupCache : ReaderWriterCache<MemberInfo, Func<TModel, TValue>> {
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100 private static Func<TModel, TValue> CreateFunc(MemberInfo member, bool isStatic) {
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101 ParameterExpression modelParam = Expression.Parameter(typeof(TModel), "model");
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102 MemberExpression memberExpr = Expression.MakeMemberAccess((!isStatic) ? modelParam : null, member);
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103 Expression<Func<TModel, TValue>> lambda = Expression.Lambda<Func<TModel, TValue>>(memberExpr, modelParam);
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104 return lambda.Compile();
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106 public Func<TModel, TValue> GetFunc(MemberInfo member, bool isStatic) {
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107 return FetchOrCreateItem(member, () => CreateFunc(member, isStatic));
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