333

MyCode.Project.Infrastructure/Specifications/ParameterRebinder.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Linq.Expressions;
+
+namespace MyCode.Project.Infrastructure
+{
+    /// <summary>
+    /// Represents the parameter rebinder used for rebinding the parameters
+    /// for the given expressions. This is part of the solution which solves
+    /// the expression parameter problem when going to Entity Framework by using
+    /// Apworks specifications. For more information about this solution please
+    /// refer to http://blogs.msdn.com/b/meek/archive/2008/05/02/linq-to-entities-combining-predicates.aspx.
+    /// </summary>
+    internal class ParameterRebinder : ExpressionVisitor
+    {
+        #region Private Fields
+        private readonly Dictionary<ParameterExpression, ParameterExpression> map;
+        #endregion
+
+        #region Ctor
+        internal ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
+        {
+            this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
+        }
+        #endregion
+
+        #region Internal Static Methods
+        internal static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
+        {
+            return new ParameterRebinder(map).Visit(exp);
+        }
+        #endregion
+
+        #region Protected Methods
+        protected override Expression VisitParameter(ParameterExpression p)
+        {
+            ParameterExpression replacement;
+            if (map.TryGetValue(p, out replacement))
+            {
+                p = replacement;
+            }
+            return base.VisitParameter(p);
+        }
+        #endregion
+    }
+}