C# .NET - Andriod App for Taking Picture and Saving it on Xamarin Studio in Windows

I am creating Andriod Application in C# Xamarin On Windows ,the app includes taking picture and save the image .
private void CreateDirectoryForPictures()
{
_dir = new Java.IO.File(Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryPictures), "AndroidCameraVSDemo");
if (!_dir.Exists())
{
_dir.Mkdirs();
}
}
But the above part of code gives me error after the solution is deployed to the device.The Error is"Java.Lang.NoSuchFieldError has been thrown".