ComboBox.Items.Clear（）不起作用

Question

我遇到了一个问题，尽管尝试了很多变通办法（其中一些也很荒谬），但我还是陷入了原点。

简单地说，我想要做的就是清除ComboBox中的项目列表。就是这样。我尝试了很多事情 - Items.Clear()，Text = String.Empty，甚至尝试了一个逐渐删除所有项目的循环 - 但没有任何效果。任何帮助将不胜感激。

以下是我的代码：

Private Sub btnDeleteCategory_Click(sender As Object, e As EventArgs) Handles btnDeleteCategory.Click
    'Clear the contents of the drop-down list with records titles.
    cboxDeleteItem.Items.Clear() ' NOT WORKING!!! NO IDEA WHY!!!
    'Set the table name depending on what category the user has selected from the drop-down list.
    Select Case cboxDeleteCategory.Text
        Case "Books"
            TableName = "tblBooks"
            Exit Select
        Case "CDs"
            TableName = "tblCDs"
            Exit Select
        Case "Movies"
            TableName = "tblMovies"
            Exit Select
        Case "TV Shows"
            TableName = "tblTVShows"
            Exit Select
        Case "Video Games"
            TableName = "tblVideoGames"
            Exit Select
    End Select
    'Connect to the corresponding table.
    ChangeTable()
    'Add all of the titles of the records into the other drop-down list.
    Do Until Incremental = MaxRows
        cboxDeleteItem.Items.Add(DataSet.Tables("Main Database").Rows(Incremental).Item("Title"))
        Incremental = Incremental + 1
    Loop
    'Reset Incremental back to 0.
    Incremental = 0
End Sub

它的工作方式是让用户从名为cboxDeleteCategory的下拉列表中选择一个类别，当用户按下btnDeleteCategory时，它应该删除cboxDeleteItem中列出的所有内容。然后它应该（最终）用它现在连接到的表的内容重新填充它 - 但是它在程序的其他地方处理;不重要。