1 files changed, 131 insertions, 0 deletions
diff --git a/src/System.Web.Mvc/ExpressionHelper.cs b/src/System.Web.Mvc/ExpressionHelper.cs
new file mode 100644
index 00000000..69432305
--- /dev/null
+++ b/src/System.Web.Mvc/ExpressionHelper.cs
@@ -0,0 +1,131 @@
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using System.Web.Mvc.ExpressionUtil;
+using System.Web.Mvc.Properties;
+
+namespace System.Web.Mvc
+{
+    public static class ExpressionHelper
+    {
+        public static string GetExpressionText(string expression)
+        {
+            return
+                String.Equals(expression, "model", StringComparison.OrdinalIgnoreCase)
+                    ? String.Empty // If it's exactly "model", then give them an empty string, to replicate the lambda behavior
+                    : expression;
+        }
+
+        public static string GetExpressionText(LambdaExpression expression)
+        {
+            // Split apart the expression string for property/field accessors to create its name
+            Stack<string> nameParts = new Stack<string>();
+            Expression part = expression.Body;
+
+            while (part != null)
+            {
+                if (part.NodeType == ExpressionType.Call)
+                {
+                    MethodCallExpression methodExpression = (MethodCallExpression)part;
+
+                    if (!IsSingleArgumentIndexer(methodExpression))
+                    {
+                        break;
+                    }
+
+                    nameParts.Push(
+                        GetIndexerInvocation(
+                            methodExpression.Arguments.Single(),
+                            expression.Parameters.ToArray()));
+
+                    part = methodExpression.Object;
+                }
+                else if (part.NodeType == ExpressionType.ArrayIndex)
+                {
+                    BinaryExpression binaryExpression = (BinaryExpression)part;
+
+                    nameParts.Push(
+                        GetIndexerInvocation(
+                            binaryExpression.Right,
+                            expression.Parameters.ToArray()));
+
+                    part = binaryExpression.Left;
+                }
+                else if (part.NodeType == ExpressionType.MemberAccess)
+                {
+                    MemberExpression memberExpressionPart = (MemberExpression)part;
+                    nameParts.Push("." + memberExpressionPart.Member.Name);
+                    part = memberExpressionPart.Expression;
+                }
+                else if (part.NodeType == ExpressionType.Parameter)
+                {
+                    // Dev10 Bug #907611
+                    // When the expression is parameter based (m => m.Something...), we'll push an empty
+                    // string onto the stack and stop evaluating. The extra empty string makes sure that
+                    // we don't accidentally cut off too much of m => m.Model.
+                    nameParts.Push(String.Empty);
+                    part = null;
+                }
+                else
+                {
+                    break;
+                }
+            }
+
+            // If it starts with "model", then strip that away
+            if (nameParts.Count > 0 && String.Equals(nameParts.Peek(), ".model", StringComparison.OrdinalIgnoreCase))
+            {
+                nameParts.Pop();
+            }
+
+            if (nameParts.Count > 0)
+            {
+                return nameParts.Aggregate((left, right) => left + right).TrimStart('.');
+            }
+
+            return String.Empty;
+        }
+
+        private static string GetIndexerInvocation(Expression expression, ParameterExpression[] parameters)
+        {
+            Expression converted = Expression.Convert(expression, typeof(object));
+            ParameterExpression fakeParameter = Expression.Parameter(typeof(object), null);
+            Expression<Func<object, object>> lambda = Expression.Lambda<Func<object, object>>(converted, fakeParameter);
+            Func<object, object> func;
+
+            try
+            {
+                func = CachedExpressionCompiler.Process(lambda);
+            }
+            catch (InvalidOperationException ex)
+            {
+                throw new InvalidOperationException(
+                    String.Format(
+                        CultureInfo.CurrentCulture,
+                        MvcResources.ExpressionHelper_InvalidIndexerExpression,
+                        expression,
+                        parameters[0].Name),
+                    ex);
+            }
+
+            return "[" + Convert.ToString(func(null), CultureInfo.InvariantCulture) + "]";
+        }
+
+        internal static bool IsSingleArgumentIndexer(Expression expression)
+        {
+            MethodCallExpression methodExpression = expression as MethodCallExpression;
+            if (methodExpression == null || methodExpression.Arguments.Count != 1)
+            {
+                return false;
+            }
+
+            return methodExpression.Method
+                .DeclaringType
+                .GetDefaultMembers()
+                .OfType<PropertyInfo>()
+                .Any(p => p.GetGetMethod() == methodExpression.Method);
+        }
+    }
+}