c# - ASP.NET 下拉列表的替代方案

Question

无论我做什么或尝试，下拉列表都不起作用，

<asp:DropDownList ID="drop1" runat="server" AutoPostBack="true" enabledviewstate="true" OnClick="Drop1_SelectedIndexChanged" />

将其绑定(bind)到此处，

  protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindDropDownList();
            }
            //drop1.SelectedIndexChanged += new EventHandler(Drop1_SelectedIndexChanged);
        }

这是永远不会触发的方法(我使用断点来检查)

protected void Drop1_SelectedIndexChanged(object sender, EventArgs e)
{
    //checkboxlist1.Items.Add("hahahha");
}

还有其他选择吗？？？？？？？？？？我需要使用填充下拉列表，

 using (SqlDataSource ds = new SqlDataSource(ConnectionString(), SelectCommand()))
            {
                System.Data.DataView dv = (System.Data.DataView)ds.Select(DataSourceSelectArguments.Empty);
                if (dv.Count > 0)
                {
                    drop1.DataSource = ds;
                    drop1.DataTextField = "UserName";
                    drop1.DataBind();
                    drop1.Items.Insert(0, "Please select a Username ");
                }
            }

Answer 1

没有为 DropDownList 定义 Click 事件。要使用的事件是 SelectedIndexChanged :

<asp:DropDownList ID="drop1" runat="server"
                  AutoPostBack="true"
                  EnabledViewState="true"
                  OnSelectedIndexChanged="Drop1_SelectedIndexChanged" />