在循环中只显示一次消息框 vb.net

Question

我有这个循环，每次条件为真时都会弹出一个消息框。

For i = 0 To DataGridView1.Rows.Count - 1
        Dim c As Boolean
        c = DataGridView1.Rows(i).Cells(0).Value
        If c = True Then
            cmd3.Connection = con
            con.Open()

            cmd3.CommandText = "insert into student select * from stud where studentno = '" & DataGridView1.Rows(i).Cells(1).Value.ToString & "' delete from stud where studentno = '" & DataGridView1.Rows(i).Cells(1).Value.ToString & "'"
            dr3 = cmd3.ExecuteReader()
            MessageBox.Show("Account approved.")
            con.Close()
        Else

        End If
    Next

消息框显示的次数与选中的行一样多。我只想展示一次。我将我的消息框重新定位到各处，但它不起作用。我搜索但没有找到答案。我试着把它移到循环外，但问题是，即使条件为假，消息框仍然显示。

谢谢！

Answer 1

一种方法是为成功批准创建一个计数器，为未成功批准创建另一个计数器，并在完成循环后显示它们。计数器在循环中递增，具体取决于每次迭代中布尔值 c 的结果。

Dim iSuccessCount As Integer
Dim iFailedCount As Integer

For i = 0 To DataGridView1.Rows.Count - 1
    Dim c As Boolean
    c = DataGridView1.Rows(i).Cells(0).Value

    If c = True Then
        iSuccessCount +=1
        cmd3.Connection = con
        con.Open()

        cmd3.CommandText = "insert into student select * from stud where studentno = '" & DataGridView1.Rows(i).Cells(1).Value.ToString & "' delete from stud where studentno = '" & DataGridView1.Rows(i).Cells(1).Value.ToString & "'"
        dr3 = cmd3.ExecuteReader()
        con.Close()
    Else
        iFailedCount += 1
    End If
Next

Dim sb As New StringBuilder

sb.Append(iSuccessCount.ToString)
sb.Append(If(iSuccessCount = 1, " account was ", " accounts were "))
sb.Append("approved.")
sb.Append(Environment.NewLine)
sb.Append(iFailedCount.ToString)
sb.Append(If(iFailedCount = 1, " account was ", " accounts were "))
sb.Append("not approved.")

MessageBox.Show(sb.ToString)

在循环中只显示一次消息框 vb.net

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