1 files changed, 30 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/IFormattable.cs b/src/mscorlib/src/System/IFormattable.cs
new file mode 100644
index 0000000000..1baf3f290e
--- /dev/null
+++ b/src/mscorlib/src/System/IFormattable.cs
@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace System {
+    
+    using System;
+    using System.Diagnostics.Contracts;
+
+    [System.Runtime.InteropServices.ComVisible(true)]
+#if CONTRACTS_FULL
+    [ContractClass(typeof(IFormattableContract))]
+#endif // CONTRACTS_FULL
+    public interface IFormattable
+    {
+        [Pure]
+        String ToString(String format, IFormatProvider formatProvider);
+    }
+
+#if CONTRACTS_FULL
+    [ContractClassFor(typeof(IFormattable))]
+    internal abstract class IFormattableContract : IFormattable
+    {
+       String IFormattable.ToString(String format, IFormatProvider formatProvider)
+       {
+           Contract.Ensures(Contract.Result<String>() != null);
+ 	       throw new NotImplementedException();
+       }
+    }
+#endif // CONTRACTS_FULL
+}