ItemTemplate ASP.NET C#中的级联DropDownList
本文关键字:级联 DropDownList ASP NET ItemTemplate | 更新日期: 2023-09-27 18:29:31
我正试图在我的ASP.NET C#web应用程序中创建一个级联下拉列表。应该发生的是,当第一个下拉列表选择的索引发生更改时,它会调用下面的代码,然后用新值填充第二个下拉列表。问题是,当我尝试填充第二个dropdownlist时,两个dropdownlists都显示为null。当我搜索控件时,似乎没有找到它们。他们在页面加载中填充Repeater的ItemTemplateField中的正确信息。我如何在没有Javascript的情况下,在Repeater中只有C#的情况下获得级联下拉列表?非常感谢您的帮助。下面的代码在显示ddl2.Items.Clear();
的行上崩溃
protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList ddl = (DropDownList) NameRepeater.FindControl("ddlCountry");
DropDownList ddl2 = (DropDownList) NameRepeater.FindControl("ddlState");
ddl2.Items.Clear();
using(SqlConnection conn = new SqlConnection(connString))
{
using(SqlCommand cmd = new SqlCommand())
{
cmd.CommandText = "SELECT State, StateID FROM States WHERE CountryID = " + ddl.SelectedValue;
cmd.Connection = conn;
conn.Open();
using(SqlDataReader sdr = cmd.ExecuteReader())
{
while (sdr.Read())
{
ListItem _listStates = new ListItem();
_listStates.Text = sdr["State"].ToString();
_listStates.Value = sdr["StateID"].ToString();
ddl2.Items.Add(_listStates);
}
}
}
}
ddl2.AppendDataBoundItems = true;
ddl2.Items.Insert(0, new ListItem("Select a State", "-1"));
ddl2.SelectedIndex = -1;
}
不要忘记调用DataBind()
,在填充下拉列表后需要它:
ddl2.DataBind();
编辑:
DropDownList ddl = (DropDownList)NameRepeater.Items[0].FindControl("ddlCountry");
DropDownList ddl2 = (DropDownList)NameRepeater.Items[0].FindControl("ddlState");