Debug 模式下运行程序的时候，Output 窗口出来个错误“A first chance exception of type 'System.ArgumentException' occurred in System.Data.dll”。 但是并没有直接throw错误。无法知道具体在哪一步发生了这个错误。
如果想知道具体的内容，需要enable 这个debug
If you do want to know, in Visual Studio -> Debug (main menu) -> Exceptions dialog, expand to the node Common Lanuage Runtime Exceptions / System / System.ArgumentException, and check the 'Thrown' CheckBox. This will cause the debugger to break then a first chance ArgumentException is happens, and then you can see more information in the exception dialog.
For more information about first and second chance exceptions please refer to this KB article: http://support.microsoft.com/kb/105675