How to do it...

The following steps will be taken to perform a direct method with an IoT device connected with IoT Hub:

1. Invoke this method from the application:

public async Task<CloudToDeviceMethodResult> InvokeDirectMethodOnDevice(string deviceId, ServiceClient serviceClient)
 {
 var methodInvocation = new CloudToDeviceMethod("WriteToMessage") { ResponseTimeout = TimeSpan.FromSeconds(300) };
 methodInvocation.SetPayloadJson("'1234567890'");

 var response = await serviceClient.InvokeDeviceMethodAsync(deviceId, methodInvocation);

 return response;
 }

1. Direct method execution on the IoT device:

deviceClient = DeviceClient.CreateFromConnectionString("", TransportType.Mqtt);

 deviceClient.SetMethodHandlerAsync("WriteToMessage", new DeviceSimulator().WriteToMessage, null).Wait();

 deviceClient.SetMethodHandlerAsync("GetDeviceName", new DeviceSimulator().GetDeviceName, new DeviceData("DeviceClientMethodMqttSample")).Wait();