1 files changed, 40 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/Runtime/CompilerServices/INotifyCompletion.cs b/src/mscorlib/src/System/Runtime/CompilerServices/INotifyCompletion.cs
new file mode 100644
index 0000000000..872a79b72b
--- /dev/null
+++ b/src/mscorlib/src/System/Runtime/CompilerServices/INotifyCompletion.cs
@@ -0,0 +1,40 @@
+// 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.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
+//
+//
+//
+// Interfaces used to represent instances that notify listeners of their completion via continuations.
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+
+using System;
+using System.Security;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Represents an operation that will schedule continuations when the operation completes.
+    /// </summary>
+    public interface INotifyCompletion
+    {
+        /// <summary>Schedules the continuation action to be invoked when the instance completes.</summary>
+        /// <param name="continuation">The action to invoke when the operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        void OnCompleted(Action continuation);
+    }
+
+    /// <summary>
+    /// Represents an awaiter used to schedule continuations when an await operation completes.
+    /// </summary>
+    public interface ICriticalNotifyCompletion : INotifyCompletion
+    {
+        /// <summary>Schedules the continuation action to be invoked when the instance completes.</summary>
+        /// <param name="continuation">The action to invoke when the operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <remarks>Unlike OnCompleted, UnsafeOnCompleted need not propagate ExecutionContext information.</remarks>
+        [SecurityCritical]
+        void UnsafeOnCompleted(Action continuation);
+    }
+}