數據綁定下拉列表，“請選擇”不起作用

Question

我試圖在添加數據綁定后將“請選擇”項添加到我的下拉列表中，但是它似乎不起作用。 這就是我正在嘗試的

ddlListMine.Items.Add(new ListItem("Please Please Please Select....", "-1"));
ddlListMine.DataSource = GetSomeChickens();
ddListMine.DataTextField = "ChickenName";
ddListMine.DataValueField= "NumberOfEggsChickenLay";
ddListMine.DataBind();

我還嘗試將第一行代碼移到最后一行，但是下拉列表的末尾出現了“ Please Please ...”項。

Answer 1

將商品插入Oth Index

    ddlListMine.DataSource = GetSomeChickens();
    ddListMine.DataTextField = "ChickenName";
    ddListMine.DataValueField= "NumberOfEggsChickenLay";
    ddListMine.Items.Insert(0, new ListItem("Please Please Please Select....", "0"));
    ddListMine.DataBind();

Answer 2

嘗試此操作，首先綁定您的數據列表，然后將一個空值listitem設置為selected。

ddlListMine.DataSource = GetSomeChickens();
ddListMine.DataTextField = "ChickenName";
ddListMine.DataValueField= "NumberOfEggsChickenLay";
ddListMine.DataBind();
ddlListMine.Items.Insert(0, new ListItem("Select Category", String.Empty));
ddListMine.SelectedIndex = 0;