你调用的对象是空的。vb.net 查找字符串
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Object reference not set to an instance of an object. vb.net looking up a string
提问by David
I'm getting this error and I don't know how to fix it. I know i'm supposed to write what I've tried, but i have no idea what to try, even after looking for a few hours about how to deal with the error.
我收到此错误，但不知道如何解决。我知道我应该写我尝试过的东西，但我不知道该尝试什么，即使在寻找了几个小时关于如何处理错误之后。
If more information is needed please let me know. Thanks
如果需要更多信息，请告诉我。谢谢
The highlighted part of the code is:
代码中突出显示的部分是：
Dim cdtrabajador As String = dgvr.Cells(0).Value.ToString
Object reference not set to an instance of an object.
你调用的对象是空的。
NullReference Exception was unhandled by user code
用户代码未处理 NullReference 异常
Private Sub PeopleDataGridView_CellFormatting(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) Handles DataGridView1.CellFormatting
If DataGridView1.RowCount > 0 AndAlso e.RowIndex > -1 Then
If e.RowIndex > -1 Then
Dim dgvr As DataGridViewRow = DataGridView1.Rows(e.RowIndex)
Dim cdtrabajador As String = dgvr.Cells(0).Value.ToString
Dim qry = From dr As PersonalObraDataSet.PersonalObRow In PersonalObraDataSet.PersonalOb Where dr.cdTrabajador = cdtrabajador
If qry.Count > 0 Then
Dim Nombre As String = qry.First.Nombre1
dgvr.Cells(1).Value = Nombre
End If
End If
End If
End Sub
回答by Kevin DiTraglia
Hard to say for sure what the root of the issue is, but you may be safe to just null check the cell before you attempt to perform any action on it, and return in the case where the cell is null. Something like:
很难确定问题的根源是什么，但是在尝试对单元格执行任何操作之前先空检查单元格可能是安全的，并在单元格为空的情况下返回。就像是：
Dim cellObj as Object = dgvr.Cells(0).Value
if Not cellObj = Nothing Then
Dim cdtrabajador As String = cellObj.ToString
'...
'Perform the rest of your code
Else
Return
Also note that if Cells(0)is actually null, invoking Valueon it may also be causing the error. If you use your debugger you should be able to pinpoint which value is null and either handle it, or look into reasons why it is null if you expect a value to be present and it isn't.
另请注意，如果Cells(0)实际上为空，则调用Value它也可能导致错误。如果您使用调试器，您应该能够查明哪个值为 null 并对其进行处理，或者如果您希望某个值存在而该值不存在，则查看其为 null 的原因。
