1 files changed, 37 insertions, 0 deletions
diff --git a/src/System.Web.Mvc/ExpressionUtil/ParameterExpressionFingerprint.cs b/src/System.Web.Mvc/ExpressionUtil/ParameterExpressionFingerprint.cs
new file mode 100644
index 00000000..5799d064
--- /dev/null
+++ b/src/System.Web.Mvc/ExpressionUtil/ParameterExpressionFingerprint.cs
@@ -0,0 +1,37 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Linq.Expressions;
+
+#pragma warning disable 659 // overrides AddToHashCodeCombiner instead
+
+namespace System.Web.Mvc.ExpressionUtil
+{
+    // ParameterExpression fingerprint class
+    // Can represent the model parameter or an inner parameter in an open lambda expression
+
+    [SuppressMessage("Microsoft.Usage", "CA2218:OverrideGetHashCodeOnOverridingEquals", Justification = "Overrides AddToHashCodeCombiner() instead.")]
+    internal sealed class ParameterExpressionFingerprint : ExpressionFingerprint
+    {
+        public ParameterExpressionFingerprint(ExpressionType nodeType, Type type, int parameterIndex)
+            : base(nodeType, type)
+        {
+            ParameterIndex = parameterIndex;
+        }
+
+        // Parameter position within the overall expression, used to maintain alpha equivalence.
+        public int ParameterIndex { get; private set; }
+
+        public override bool Equals(object obj)
+        {
+            ParameterExpressionFingerprint other = obj as ParameterExpressionFingerprint;
+            return (other != null)
+                   && (this.ParameterIndex == other.ParameterIndex)
+                   && this.Equals(other);
+        }
+
+        internal override void AddToHashCodeCombiner(HashCodeCombiner combiner)
+        {
+            combiner.AddInt32(ParameterIndex);
+            base.AddToHashCodeCombiner(combiner);
+        }
+    }
+}