C# 更改dropdownlist中继器内容目录中的索引值

我想根据dropdownlist选择的索引在中继器中显示数据。例如，当我在dropdownlist中选择“帮助”项时，中继器将在数据库中显示帮助类别内容。否则，选择汽车将显示汽车类别。我可以知道如何控制我的下拉列表吗

if (!IsPostBack)
        {
            try
            {
                MySqlConnection connStr = new MySqlConnection();
                connStr.ConnectionString = "Server = localhost; Database = healthlivin; Uid = root; Pwd = khei92;";
                String stSearch = "SELECT t.title, p.userName, t.threadID FROM thread t , person p WHERE p.PersonID = t.PersonID AND t.categories = @categories";
                MySqlCommand cmdSearch = new MySqlCommand(stSearch, connStr);
                cmdSearch.Parameters.AddWithValue("@categories", categoriesDropDownList.SelectedValue);

                connStr.Open();

                MySqlDataReader dtrRead = cmdSearch.ExecuteReader();
                categoriesRepeater.DataSource = dtrRead;
                categoriesRepeater.DataBind();
                dtrRead.Close();
                dtrRead = null;
                //MessageBox.Show("Connected");
                connStr.Close();
            }
            catch (Exception ex)
            {
                //MessageBox.Show("X Connected" + ex.ToString());
            }


        } 

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您必须创建下拉列表的

AutoPostBack=“true”

，并绑定

SelectedIndexChanged

事件，从中获取selectedIndex并使用它绑定中继器

Html

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嗯~对不起。。。是否我必须为每个selectedIndex编写select查询？因为我有10个类别。

<asp:DropDownList ID="ddl" runat="server" AutoPostBack="True" 
    onselectedindexchanged="itemSelected">
</asp:DropDownList>

protected void itemSelected(object sender, EventArgs e)
{
    if(ddl.SelectedIndex == 1)
    {
        //Bind Help   
    }        
    else
    if(ddl.SelectedIndex == 2)
    {
        //Bind Car
    }        
}