Please install package: \'Xamarin.Android.Support.Design\' available in SDK installer. Android resource directory C:\\Users\\Srinivasarao\\AppData\\Local\\Xamarin\\Andro
To launch the Android SDK on Windows, navigate to the Tools > Android menu and select Open Android SDK Manager.
The SDK Manager window will open.
You can use this Android SDK manager to select tools, documentation, and the SDK that you wish to download or update.
Ref: https://developer.xamarin.com/recipes/cross-platform/ide/launch_sdk_manager/
1) Delete the "21.0.3" folder within in your AppData dir (reference your error)
2) Rebuild your application.