请帮助无法解决由于应用程序崩溃而导致问题存在的位置，但数据库中的数据会更新 [英] please help not able to tress where the issue exists as application crashes but data gets updated in database

问题描述

亲爱的团队，

我正在尝试以vb格式从datagridview批量插入sql数据库，数据已按预期成功以正确的格式插入数据库中，但在运行时出现null引用异常.

请帮忙.！我的代码在这里..

Dear Team,

I am trying to do bulk insert from datagridview in vb form to sql database , the data is sucessfully inserted into the database in correct format as expected, but getting a null reference exception at runtime.

Please help.! My code goes here..

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
For Each row As DataGridViewRow In Form2.DataGridView1.Rows


If row.State > DataGridViewElementStates.None Then
    Dim nItem As String = row.Cells("Col1").Value.ToString()
    Dim nQty As String = row.Cells("Col2").Value.ToString()
    Dim nMrp As String = row.Cells("Col3").Value.ToString()
    Dim nRate As String = row.Cells("Col4").Value.ToString()
    Dim nAmount As String = row.Cells("Col5").Value.ToString()
    Dim nBillNo As String = Form2.TextBox3.Text
    Dim nTransactionDate As String = DateValue(Now)
    Dim nTransactionTime As String = TimeValue(Now)
    Dim nUserName As String = Form2.TextBox5.Text

    Try

        Using connection As New SqlClient.SqlConnection("Server=.;UID=user; PWD=pwd")
            Using cmd As New SqlClient.SqlCommand("GetTransaction", connection)


                With cmd
                    .CommandType = CommandType.StoredProcedure
                    .Parameters.AddWithValue("@nItem", nItem)
                    .Parameters.AddWithValue("@nQty", nQty)
                    .Parameters.AddWithValue("@nMrp", nMrp)
                    .Parameters.AddWithValue("@nRate", nRate)
                    .Parameters.AddWithValue("@nAmount", nAmount)
                    .Parameters.AddWithValue("@nBillNo", nBillNo)
                    .Parameters.AddWithValue("@nTransactionDate", nTransactionDate)
                    .Parameters.AddWithValue("@nTransactionTime", nTransactionTime)
                    .Parameters.AddWithValue("@nUserName", nUserName)

                    .Prepare()

                    connection.Open()
                    .ExecuteNonQuery()
                End With
            End Using
        End Using
    Catch ex As NullReferenceException
        MsgBox(ex.Message)
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End If

推荐答案

原因是，当DataGridView.AllowUserToAddRows设置为True(默认情况下设置为True)时，在DataGridView的末尾会有一个 empty Row.当使用For Each循环迭代Rows 集合时，对于每一行，将执行存储过程，并在数据库中更新数据.当到达DataGridView的最后一个空行时，会抛出NullReference 异常.
如果在For Each循环之前将DataGridView.AllowUserToAddRows设置为False ，则可能不会引发上述异常.

The reason is that when the DataGridView.AllowUserToAddRows is set toTrue, which is by default set to True, then there will be an empty Row at the end of the DataGridView. When the Rows collection is iterated using the For Each loop, for each row the the Stored procedure is executed and the data is updated in the database. When the last empty row of the DataGridView is reached NullReference exception is thrown.
If DataGridView.AllowUserToAddRows is set to False before the For Each loop, the above exception may not be thrown.

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