Question

我正在尝试创建一个登录表单并继续收到此错误：

Visual Basic System.Data.OleDb.OleDbException：'没有给出一个值或更多必需参数。'

我正在使用带vb的访问数据库，所有内容拼写正确，但我一直收到此错误？

Private Sub Btn_Login_Click(sender As Object, e As EventArgs) Handles Btn_Login.Click
    If DbConnect() Then
        Dim SQLCmd As New OleDbCommand
        With SQLCmd
            .Connection = cn
            .CommandText = "Select * From Tbl_Staff Where (Username = @sUsername) and (Password = @sPassword)"
            .Parameters.AddWithValue("@sUsername", Txt_Username.Text)
            .Parameters.AddWithValue("@sPassword", Txt_Password.Text)

            Dim rs As OleDbDataReader = .ExecuteReader()

            If rs.Read Then
                PublicFirstname = rs("Firstname")
                PublicStaffID = rs("StaffID")
                'PublicAccessLevel = rs("AccessLevel")
                frmMainMenu.Show()
            Else
                MsgBox("Sorry, incorrect log in details entered")
            End If
            rs.Close()

修改
更改了我的代码，但仍然收到同样的错误：

If DbConnect() Then
    Using SQLCmd As New OleDbCommand
        With SQLCmd
            .Connection = cn
            .CommandText = "Select * From Tbl_Staff Where (Username = ?) and ([Password] = ?)"
            .Parameters.Add("@sUsername", OleDbType.VarChar).Value = Txt_Username.Text
            .Parameters.Add("@sPassword", OleDbType.VarChar).Value = Txt_Password.Text

            Using rs As OleDbDataReader = .ExecuteReader()
                If rs.Read Then
                Else
                    MsgBox("Sorry, incorrect log in details entered")
                End If
                rs.Close()
            End Using
        End With
    End Using
End If

Answer 1

我在这里看到两个问题。

OleDbCommand不支持将CommandType设置为Text的命名参数。
提供的订单非常丰富。
PASSWORD是ms-access中的保留字。
将其放在方括号中。

其他需要加强的事情。

对Using和OleDbCommand。

OleDbDataReader

不要以明文形式存储密码。

所以你的代码应如下所示：

Using SQLCmd As New OleDbCommand
    With SQLCmd
        .Connection = cn
        .CommandText = "Select * From Tbl_Staff Where (Username = ?) and ([Password] = ?)"
        .Parameters.Add("@sUsername", OleDbType.VarChar).Value = Txt_Username.Text
        .Parameters.Add("@sPassword", OleDbType.VarChar).Value = Txt_Password.Text

        Using rs As OleDbDataReader = .ExecuteReader()
            If rs.Read Then
            Else
                MsgBox("Sorry, incorrect log in details entered")
            End If
            rs.Close()
        End Using
    End With
End Using

修改
由于列名不是Username和Password，而是sUsername和sPassword，您必须更改CommandText，如下所示：

.CommandText = "Select * From Tbl_Staff Where (sUsername = ?) and (sPassword = ?)"

Visual Basic System.Data.OleDb.OleDbException：'没有给出一个或多个必需参数的值。'

1 个答案: