1 files changed, 47 insertions, 0 deletions
diff --git a/src/System.Web.Mvc/ExpressionUtil/ExpressionFingerprint.cs b/src/System.Web.Mvc/ExpressionUtil/ExpressionFingerprint.cs
new file mode 100644
index 00000000..1d9cf5e2
--- /dev/null
+++ b/src/System.Web.Mvc/ExpressionUtil/ExpressionFingerprint.cs
@@ -0,0 +1,47 @@
+using System.Linq.Expressions;
+
+namespace System.Web.Mvc.ExpressionUtil
+{
+    // Serves as the base class for all expression fingerprints. Provides a default implementation
+    // of GetHashCode().
+
+    internal abstract class ExpressionFingerprint
+    {
+        protected ExpressionFingerprint(ExpressionType nodeType, Type type)
+        {
+            NodeType = nodeType;
+            Type = type;
+        }
+
+        // the type of expression node, e.g. OP_ADD, MEMBER_ACCESS, etc.
+        public ExpressionType NodeType { get; private set; }
+
+        // the CLR type resulting from this expression, e.g. int, string, etc.
+        public Type Type { get; private set; }
+
+        internal virtual void AddToHashCodeCombiner(HashCodeCombiner combiner)
+        {
+            combiner.AddInt32((int)NodeType);
+            combiner.AddObject(Type);
+        }
+
+        protected bool Equals(ExpressionFingerprint other)
+        {
+            return (other != null)
+                   && (this.NodeType == other.NodeType)
+                   && Equals(this.Type, other.Type);
+        }
+
+        public override bool Equals(object obj)
+        {
+            return Equals(obj as ExpressionFingerprint);
+        }
+
+        public override int GetHashCode()
+        {
+            HashCodeCombiner combiner = new HashCodeCombiner();
+            AddToHashCodeCombiner(combiner);
+            return combiner.CombinedHash;
+        }
+    }
+}