mcs/class/System.Web.Mvc2/System.Web.Mvc/ExpressionHelper.cs

   1 /* ****************************************************************************\r
   2  *\r
   3  * Copyright (c) Microsoft Corporation. All rights reserved.\r
   4  *\r
   5  * This software is subject to the Microsoft Public License (Ms-PL). \r
   6  * A copy of the license can be found in the license.htm file included \r
   7  * in this distribution.\r
   8  *\r
   9  * You must not remove this notice, or any other, from this software.\r
  10  *\r
  11  * ***************************************************************************/\r
  12 \r
  13 namespace System.Web.Mvc {\r
  14     using System;\r
  15     using System.Collections.Generic;\r
  16     using System.Globalization;\r
  17     using System.Linq;\r
  18     using System.Linq.Expressions;\r
  19     using System.Reflection;\r
  20     using System.Web.Mvc.Resources;\r
  21 \r
  22     public static class ExpressionHelper {\r
  23         public static string GetExpressionText(string expression) {\r
  24             return\r
  25                 String.Equals(expression, "model", StringComparison.OrdinalIgnoreCase)\r
  26                     ? String.Empty    // If it's exactly "model", then give them an empty string, to replicate the lambda behavior\r
  27                     : expression;\r
  28         }\r
  29 \r
  30         public static string GetExpressionText(LambdaExpression expression) {\r
  31             // Crack the expression string for property/field accessors to create its name\r
  32             Stack<string> nameParts = new Stack<string>();\r
  33             Expression part = expression.Body;\r
  34 \r
  35             while (part != null) {\r
  36                 if (part.NodeType == ExpressionType.Call) {\r
  37                     MethodCallExpression methodExpression = (MethodCallExpression)part;\r
  38 \r
  39                     if (!IsSingleArgumentIndexer(methodExpression)) {\r
  40                         break;\r
  41                     }\r
  42 \r
  43                     nameParts.Push(\r
  44                         GetIndexerInvocation(\r
  45                             methodExpression.Arguments.Single(),\r
  46                             expression.Parameters.ToArray()\r
  47                         )\r
  48                     );\r
  49 \r
  50                     part = methodExpression.Object;\r
  51                 }\r
  52                 else if (part.NodeType == ExpressionType.ArrayIndex) {\r
  53                     BinaryExpression binaryExpression = (BinaryExpression)part;\r
  54 \r
  55                     nameParts.Push(\r
  56                         GetIndexerInvocation(\r
  57                             binaryExpression.Right,\r
  58                             expression.Parameters.ToArray()\r
  59                         )\r
  60                     );\r
  61 \r
  62                     part = binaryExpression.Left;\r
  63                 }\r
  64                 else if (part.NodeType == ExpressionType.MemberAccess) {\r
  65                     MemberExpression memberExpressionPart = (MemberExpression)part;\r
  66                     nameParts.Push("." + memberExpressionPart.Member.Name);\r
  67                     part = memberExpressionPart.Expression;\r
  68                 }\r
  69                 else {\r
  70                     break;\r
  71                 }\r
  72             }\r
  73 \r
  74             // If it starts with "model", then strip that away\r
  75             if (nameParts.Count > 0 && String.Equals(nameParts.Peek(), ".model", StringComparison.OrdinalIgnoreCase)) {\r
  76                 nameParts.Pop();\r
  77             }\r
  78 \r
  79             if (nameParts.Count > 0) {\r
  80                 return nameParts.Aggregate((left, right) => left + right).TrimStart('.');\r
  81             }\r
  82 \r
  83             return String.Empty;\r
  84         }\r
  85 \r
  86         private static string GetIndexerInvocation(Expression expression, ParameterExpression[] parameters) {\r
  87             Expression converted = Expression.Convert(expression, typeof(object));\r
  88             ParameterExpression fakeParameter = Expression.Parameter(typeof(object), null);\r
  89             Expression<Func<object, object>> lambda = Expression.Lambda<Func<object, object>>(converted, fakeParameter);\r
  90             Func<object, object> func;\r
  91 \r
  92             try {\r
  93                 func = ExpressionUtil.CachedExpressionCompiler.Process(lambda);\r
  94             }\r
  95             catch (InvalidOperationException ex) {\r
  96                 throw new InvalidOperationException(\r
  97                     String.Format(\r
  98                         CultureInfo.CurrentUICulture,\r
  99                         MvcResources.ExpressionHelper_InvalidIndexerExpression,\r
 100                         expression,\r
 101                         parameters[0].Name\r
 102                     ),\r
 103                     ex\r
 104                 );\r
 105             }\r
 106 \r
 107             return "[" + Convert.ToString(func(null), CultureInfo.InvariantCulture) + "]";\r
 108         }\r
 109 \r
 110         internal static bool IsSingleArgumentIndexer(Expression expression) {\r
 111             MethodCallExpression methodExpression = expression as MethodCallExpression;\r
 112             if (methodExpression == null || methodExpression.Arguments.Count != 1) {\r
 113                 return false;\r
 114             }\r
 115 \r
 116             return methodExpression.Method\r
 117                                    .DeclaringType\r
 118                                    .GetDefaultMembers()\r
 119                                    .OfType<PropertyInfo>()\r
 120                                    .Any(p => p.GetGetMethod() == methodExpression.Method);\r
 121         }\r
 122     }\r
 123 }\r