Getting error while creating running sample QuickStart code: Sample: Create, retrieve, update, and delete a dashboard

I am follow https://msdn.microsoft.com/en-us/library/gg334617.aspx for  Create, retrieve, update, and delete a dashboard.

I am getting error while executing following line in file : SampleCode\CS\VisualizationsAndDashboards\CRUDDashboards.cs

_dashboardId = _serviceProxy.Create(dashboard);