1 files changed, 22 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/Runtime/CompilerServices/ITuple.cs b/src/mscorlib/src/System/Runtime/CompilerServices/ITuple.cs
new file mode 100644
index 0000000000..cafee11f8a
--- /dev/null
+++ b/src/mscorlib/src/System/Runtime/CompilerServices/ITuple.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// This interface is required for types that want to be indexed into by dynamic patterns.
+    /// </summary>
+    public interface ITuple
+    {
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int Length { get; }
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object this[int index] { get; }
+    }
+}