datagridview 不使用组合框 vb.net 清除数据

Question

当我从组合框中选择项目时，我使项目具有组合框项目，它是从具有不同列的同一个表中的 datagridview 中查看数据 问题是当我从组合框数据网格查看数据中选择项目时，当我选择另一个项目表单组合框数据网格视图新列和旧列时

这是我的代码：

Dim sqlconn As New SqlConnection(con) 
Dim comm As New SqlCommand 
'Dim comm2 As New SqlCommand
Dim sql As String = "select * from entsab"
Dim adpt As New SqlDataAdapter(Sql, con)
Dim ds As New DataSet()
Dim dr As SqlDataReader 
Dim dr2 As SqlDataReader
Dim dt As New DataTable
Private Sub ComboBox2_SelectedValueChanged(sender As Object, e As EventArgs) Handles ComboBox2.SelectedValueChanged, ComboBox3.SelectedValueChanged
    Select Case ComboBox2.SelectedItem
        Case ComboBox2.Items.Item(0) '1
            dt.Clear()
            Dim comm2 As New SqlCommand
            comm2.CommandText = Nothing
            DGV1.Refresh()
            comm2.CommandText = "select l1,sub_code,sub_name,houres from sub_with_sct where sction_ID=1"
            comm2.Connection = sqlconn
            sqlconn.Open()
            dr2 = comm2.ExecuteReader
            dt.Load(dr2)
            DGV1.AutoGenerateColumns = True
            DGV1.DataSource = dt
            DGV1.Refresh()
            sqlconn.Close()
            DGV1.Visible = True
            comm2.Dispose()
        Case ComboBox2.Items.Item(1)
            dt.Clear()
            Dim comm2 As New SqlCommand
            DGV1.DataSource = Nothing
            DGV1.Columns.Clear()
            comm2.CommandText = Nothing
            DGV1.Refresh()
            comm2.CommandText = "select l2,sub_code,sub_name,houres from sub_with_sct where sction_ID=1"
            comm2.Connection = sqlconn
            sqlconn.Open()
            dr2 = comm2.ExecuteReader
            dt.Load(dr2)
            DGV1.AutoGenerateColumns = True
            DGV1.DataSource = dt
            DGV1.Refresh()
            sqlconn.Close()
            DGV1.Visible = True
            comm2.Dispose()
    End Select
End Sub

当我选择第一项时：

当我选择第二个项目时：

Answer 1

尝试将：DGV1.Columns.Clear() 添加到您的第一个 案子 。并在所有情况下使用dt= New DataTable() 而不是dt.Clear()。