Hi Jiang,
This problem typically happens when an addin built from an older version of the WPF SDK is opened in a machine with a newer version of the SDK. You can try to fix the csproj file and update the reference dll to work around the porblem:
Update the csproj file:
1. Open the WeatherUndergroundWidgetCS project your downloaded in Visual Studio
2. On Solution Explorer, right click on the project (not the solution), click Unload Project
3. The project name becomes WeatherUndergroundWidgetCS (unavailable), right click on it again then click Edit WeatherUndergroundWidgetCS.csproj
4. The .csproj file opens as plain xml text. Then look up for the <ReferenceFolder32>, <ReferenceFolder64>, <IDEIntegrationFolder32> and <IDEIntegrationFolder64> tags. In each of them you will see a piece of text like "ArcGISRuntimeWPF10.1.1@InstallDir". Replace the version number (e.g. 10.1.1) to your SDK's version (10.2.3)
5. When 4 places above have been updated and saved, right click on WeatherUndergroundWidgetCS (unavailable), click Reload Project
Update the reference dll:
6. When the project is reloaded, open "References" to see its reference dlls
7. Remove ESRI.ArcGIS.OperationsDashboard.dll (which should appear broken)
8. Add the dll back from the Ops Dashboard bin folder that comes with the SDK, typically it resides in:
c:\Program Files (x86)\ArcGIS SDKs\WPF10.2.3\sdk\OperationsDashboard\ESRI.ArcGIS.OperationsDashboard.dll
9. Set the Copy Local property of the dll above to False
10. Rebuild the project.
Please let me know if that helps,
Tif
