錯訊排除 : Exception has been thrown by the target of an invocation. The original message is 'Index and length must refer to a location within the string.

中文 : 索引和長度必須參考字串中的位置。\r\n參數名稱: length

英文 : Exception has been thrown by the target of an invocation. The original message is 'Index and length must refer to a location within the string. Parameter name: length'.

原因:String.Substring(0, 4)要取用的結束長度比原字串還長