Variable 'X' is used before it has been assigned a value. A null reference exception could result at runtime.
在自己做机房收费系统的过程中出现了这样的一个现象:如图str1下面出现了一行波浪线.同时提醒自己错出现的错误.提示如下:Variable'str1'isusedbeforeithasbeenassignedavalue.Anullreferenceexceptioncouldresultatruntime