没有为一个或多个所需参数给出值- Excel

sql1 = "SELECT distinct(Area) FROM (" + tablename + ")"
        Dim ds_area As New DataSet
        Dim da_area As New OleDb.OleDbDataAdapter(sql1, MyConnection)
        da_area.Fill(ds_area)
        Me.ListBox1.DataSource = Nothing
        Me.ListBox1.Items.Clear()
        Me.ListBox1.DataSource = ds_area.Tables(0)
        Me.ListBox1.DisplayMember = "Area"
        Me.ListBox1.ValueMember = "Area"
        Me.ListBox1.SelectedIndex = 0
        Me.cmbArea.Items.Insert(0, "Select All")
        For i = 0 To ds_area.Tables(0).Rows.Count() - 1
            Me.cmbArea.Items.Add(ds_area.Tables(0).Rows(i)(0).ToString)
        Next
        Me.cmbArea.SelectedIndex = 0
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

错误报告显示"No value given for一个或多个必需的参数"