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Question

有人可以帮助我吗？我在登录时遇到了一些问题。当我尝试登录时，我收到错误“多步 OLE DB 操作生成错误。检查每个 OLE DB 状态值（如果可用）。没有完成任何工作。” - 结合 ExecuteScalar 检索。

提前感谢您提供的任何帮助，您可能会或可能无法给我。

 Protected Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click

    If String.IsNullOrWhiteSpace(txtUsername.Text) Then
        Invalid()
        Exit Sub
    End If

    Using con As New OleDbConnection(connectionString)
        Dim cmd As New OleDbCommand("Select count(*) From tblAccounts where Username = ?", con)
        cmd.Parameters.AddWithValue("Username", txtUsername)
        con.Open()

        If CType(cmd.ExecuteScalar(), Integer) > 0 Then
            cmd.CommandText = "Select CPassword From tblAccounts Where Username = ?"
            Dim matches As String = CType(cmd.ExecuteScalar(), String)
            If matches = Sha1(txtPassword.Text) Then
                Response.Redirect("main.aspx")
            Else
                Invalid()
            End If
        Else
            Invalid()
        End If
    End Using

 End Sub

Answer 1

首先，我建议（已经建议），您重新检查连接字符串...

就个人而言，我不会重复使用相同的OleDbCommand，因为这可能会导致不良结果。相反，我会尝试以下方法：

Protected Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click

    If Not String.IsNullOrWhiteSpace(txtUsername.Text) Then

        Using con As New OleDbConnection(ConnectionString)
            con.Open()

            Dim Result As Integer = 0

            Using cmd As New OleDbCommand("Select count(*) From tblAccounts where Username = @Username", con)
                cmd.Parameters.AddWithValue("@Username", txtUsername.text)

                Result = CInt(cmd.ExecuteScalar)
            End Using

            If Result > 0 Then
                Using cmd As New OleDbCommand("Select CPassword From tblAccounts Where Username = @Username", con)
                    cmd.Parameters.AddWithValue("@Username", txtUsername.text)

                    Dim Obj As Object = cmd.ExecuteScalar()

                    If (Obj IsNot Nothing) AndAlso (Obj IsNot DBNull.Value) Then
                        Dim matches As String = Obj.ToString

                        If matches = SHA1(txtPassword.Text) Then
                            Response.Redirect("main.aspx")
                            Exit Sub
                        End If

                    End If

                End Using
            End If

        End Using

    End If

    Invalid()

End Sub

希望这可以帮助