Update quickstart-control-device-dotnet.md

Document was edited 03/03 for CLI changes as well as 03/04 for adding a note.  ms.date should be updated to note that the document is up to date and kept fresh.


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cc: @robinsh

Author: spboyer

articles/iot-hub/quickstart-control-device-dotnet.md

@@ -9,7 +9,7 @@ services: iot-hub
 ms.devlang: csharp
 ms.topic: quickstart
 ms.custom: mvc
-ms.date: 06/21/2019
+ms.date: 03/04/2020
 # As a developer new to IoT Hub, I need to see how to use a back-end application to control a device connected to the hub.
 ---