I get an unhandled Exception:

System.MissingMethodException: Method not found: 'System.IO.Stream Microsoft.SharePoint.SPFile.OpenBinaryStream(Microsoft.SharePoint.SPOpenBinaryOptions)'.
   at MigrateWorkflow.formMain.ddlWorkflow_SelectedIndexChanged(Object sender, EventArgs e)
   at System.Windows.Forms.ComboBox.OnSelectedIndexChanged(EventArgs e)
   at System.Windows.Forms.ComboBox.WmReflectCommand(Message& m)
   at System.Windows.Forms.ComboBox.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)