用ms-access数据库在vb.net中进行选择

我想在我的表中选择一些数据，我使用以下代码：

Public Class frmLogin
Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOK.Click
            Dim t As New DataTable
    Dim adapter As OleDbDataAdapter = New OleDbDataAdapter()
    Dim cmd As OleDbCommand
    Dim reader As OleDbDataReader = Nothing
    Dim tuser As String = txtUsername.Text

    Dim sql As String = "SELECT * FROM dosen WHERE nip=tuser"
    Try
        cmd = New OleDbCommand(sql, conn)
        reader = cmd.ExecuteReader()

        While reader.Read
            MessageBox.Show(reader.GetString(0).ToString & _
                            vbTab & vbTab & reader.GetString(1).ToString)
        End While
    Finally
        If reader IsNot Nothing Then reader.Close()
    End Try

End Sub

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但是

reader=cmd.ExecuteReader（）

行中有一个错误。有人能帮我吗？

纠正错误。代码应该是

Dim reader As OleDbDataReader ' no need for nothing
Dim adapter As New OleDbDataAdapter()
Dim sql As String = "SELECT * FROM dosen WHERE nip='" & tuser & "'"

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tuser是一个变量，而不是content

，其中是ur连接字符串。