Question

由于此错误，我无法运行我的程序。有人能帮助我吗？感谢。

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Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    If tbx_username.Text <> "" And tbx_pass.Text <> "" Then
        Dim SM As New SubjectMaintenance
        Dim dr = SM.openSel(SqlString.getSQLSelect(Account.tablename, Account.si_data_username & "='" & tbx_username.Text & "' and " & Account.si_data_pwd & "='" & tbx_pass.Text & "'"), CommandType.Text)

        While dr.Read
            GUI.accnt.pData_id = dr(Account.si_data_id)
            Me.Hide()
            GUI.Show()
    **Else**

            GUI.accnt.pData_pwd = dr(Account.si_data_pwd)
            GUI.accnt.pData_username = dr(Account.si_data_username)
            GUI.accnt.pData_lname = dr(Account.si_data_lname)
            GUI.accnt.pData_fname = dr(Account.si_data_fname)
            GUI.accnt.pData_mname = dr(Account.si_data_mname)
        End While
        SM.closeConDr()
        If GUI.accnt.pData_id > 0 Then
            MessageBox.Show("Login Failed!")
        End If
    End If
End Sub

结束班

Answer 1

您无法将else置于while end-while内，if-else-end if和while-end while是独立声明，因此您可以按以下方式混合使用：

while
 if
 else
 end if
end while

或

if
 while
 end while
else
 while
 end while
end if

进入嵌套语句的唯一方法是GoTo语句，它将指令指针无条件地移动到指定的标签。

Answer 2

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
If tbx_username.Text <> "" And tbx_pass.Text <> "" Then
    Dim SM As New SubjectMaintenance
    Dim dr = SM.openSel(SqlString.getSQLSelect(Account.tablename, Account.si_data_username & "='" & tbx_username.Text & "' and " & Account.si_data_pwd & "='" & tbx_pass.Text & "'"), CommandType.Text)

    While dr.Read
        GUI.accnt.pData_id = dr(Account.si_data_id)
        Me.Hide()
        GUI.Show()

    End While
**Else**  'Try moving the else below the end while or above the while

        GUI.accnt.pData_pwd = dr(Account.si_data_pwd)
        GUI.accnt.pData_username = dr(Account.si_data_username)
        GUI.accnt.pData_lname = dr(Account.si_data_lname)
        GUI.accnt.pData_fname = dr(Account.si_data_fname)
        GUI.accnt.pData_mname = dr(Account.si_data_mname)
    SM.closeConDr()
    If GUI.accnt.pData_id > 0 Then
        MessageBox.Show("Login Failed!")
    End If
  End If
End Sub

'尝试在while时或上方移动其他位置

'Else'必须先匹配'If'或'ElseIf'

2 个答案: