如何在radcombobox中选择默认项目

Question

在我的应用程序中，有一个Radcombobox自动完成功能，以及一个查询SQL，该SQL在键入时会加载数据库的寄存器，这项工作有效，但是当我不选择Radcombobox的任何选项时，它的想法是使用查询加载所有寄存器Select * From mytable，但是不起作用。

这是代码，我尝试放入IF来验证Radcombobox的值。 我希望从Radcombobox中选择一个选项时，从DB加载所有寄存器

Radcombobox代码：

<telerik:RadComboBox RenderMode="Lightweight"
                     ID="RadComboBox1"
                     runat="server"
                     EmptyMessage="Select Classification"
                     EnableLoadOnDemand="True"
                     ShowMoreResultsBox="true"
                     EnableVirtualScrolling="true"
                     style="width: 238px"
                     OnItemsRequested="RadComboBox1_ItemsRequested">
</telerik:RadComboBox>

功能加载代码：

Public Function GetData(text As String) As DataTable

    Dim dbConn As MySqlConnection
    Dim connStr As String = Nothing
    Dim sqlQuery As String = Nothing
    Dim table As New DataTable

    connStr = ConfigurationManager.ConnectionStrings("db").ConnectionString
    dbConn = New MySqlConnection(connStr)
    dbConn.Open()
    If RadComboBox1.SelectedValue = "Select Classification" Then

        Dim consulta As New MySqlDataAdapter("SELECT * from t_clasificacion", ConfigurationManager.ConnectionStrings("db").ConnectionString)
        consulta.Fill(table)
    Else

        Dim consulta As New MySqlDataAdapter("SELECT * from t_clasificacion where nombre_clasif LIKE '%' @text '%'", ConfigurationManager.ConnectionStrings("db").ConnectionString)
        consulta.SelectCommand.Parameters.AddWithValue("@text", text)
        consulta.Fill(table)
    End If
    Return table

End Function

Private Shared Function GetStatusMessage(offset As Integer, total As Integer) As String
    If total <= 0 Then
        Return "No matches"
    End If

    Return [String].Format("Items <b>1</b>-<b>{0}</b> out of <b>{1}</b>", offset, total)
End Function


Private Const ItemsPerRequest As Integer = 10
Protected Sub RadComboBox1_ItemsRequested(sender As Object, e As RadComboBoxItemsRequestedEventArgs)

    Dim data As DataTable = GetData(e.Text)

    Dim itemOffset As Integer = e.NumberOfItems
    Dim endOffset As Integer = Math.Min(itemOffset + ItemsPerRequest, data.Rows.Count)
    e.EndOfItems = endOffset = data.Rows.Count

    For i As Integer = itemOffset To endOffset - 1
        RadComboBox1.Items.Add(New RadComboBoxItem(data.Rows(i)("nombre_clasif").ToString(), data.Rows(i)("IdClasif").ToString()))
    Next

    e.Message = GetStatusMessage(endOffset, data.Rows.Count)

End Sub

我的radcmbx的图片