asp.net – 下拉列表重置SelectedValue

我有一个连接到ObjectDataSource的DropDownList.在我的页面加载中,我根据具体情况将s??electedvalue设置为特定值.如何在我的方法中选择索引以“重置”所选值,以便您仍然可以从其他选项中进行选择？或者我不应该使用selectedvalue来设置下拉列表的默认值？

<asp:DropDownList ID="DropDownList" runat="server" DataSourceID="ObjectDataSource" DataTextField="Type" DataValueField="TypeId" 
    AutoPostBack="true" onselectedindexchanged="DropDownList_SelectedIndexChanged" >
            </asp:DropDownList>

protected void Page_Load(object sender,EventArgs e)
{
        int default = category.TypeId;
        DropDownList.SelectedIndex = default;

}

protected void DropDownList_SelectedIndexChanged(object sender,EventArgs e)
{

    int id = int.Parse(DropDownList.SelectedValue);
    Session["id"] = id;
}

protected void Page_Load(Object sender,EventArgs e)
{
    if(!IsPostBack)
    {
        int default = category.TypeId;
        DropDownList.SelectedValue = default.ToString();
    }
}