我不明白为什么我会收到以下错误:
NullReference Exception was unhandled by user code
Object reference not set to an instance of an object.
来自以下代码:
Dim repNumber As String
If Not (gridView.GetFocusedRowCellValue("RepNo").ToString.Trim = Nothing) Then
repNumber = gridView.GetFocusedRowCellValue("RepNo").ToString.Trim
Else
MessageBox.Show("repNumber is empty!")
repNumber = repCurrent
End If
这条线在做什么? (验证值是否为NULL(或NOT NULL)):
If Not (gridView.GetFocusedRowCellValue("RepNo").ToString.Trim = Nothing) Then
(上一行是给我错误的那一行)
答案 0 :(得分:-1)
" NULL"并且"没什么"不是一回事....你需要这样做。
Dim repNumber As String
If (gridView.GetFocusedRowCellValue("RepNo") is dbnull.value) Then
MessageBox.Show("repNumber is empty!")
repNumber = repCurrent
Else
repNumber = gridView.GetFocusedRowCellValue("RepNo").ToString.Trim
End If
"没有什么"是指尚未实例化的对象...." Dbnull.value"是指从数据库中读取的空值....