C# dropdownlist无法识别listitem
我有一个dropdownlist,它的填充由下面显示的函数完成-:C# dropdownlist无法识别listitem,c#,asp.net,drop-down-menu,C#,Asp.net,Drop Down Menu,我有一个dropdownlist,它的填充由下面显示的函数完成-: public void filldropdown() { MySqlConnection conn = new MySqlConnection(connectionString); conn.Open(); string query = "select * from category"; MySqlCommand cmd = new MySqlCommand(query,conn); My
public void filldropdown()
{
MySqlConnection conn = new MySqlConnection(connectionString);
conn.Open();
string query = "select * from category";
MySqlCommand cmd = new MySqlCommand(query,conn);
MySqlDataReader dr = cmd.ExecuteReader();
if(dr.HasRows)
{
DropDownList1.Items.Add(new ListItem("---select---","null"));
while(dr.Read())
{
DropDownList1.DataSource = dr;
DropDownList1.DataTextField = "name";
DropDownList1.DataValueField = "id";
DropDownList1.DataBind();
}
}
conn.Close();
}
aspx中的下拉列表为-:
<asp:DropDownList OnSelectedIndexChanged="showlabel" AutoPostBack="true" ID="DropDownList1" runat="server">
<asp:ListItem Text="---select---" Value="null"></asp:ListItem>
</asp:DropDownList>
我只是不知道第一个项目是如何从数据库中出来的,而不是“---选择--”
谢谢您的时间。您已经更改了数据源:
DropDownList1.DataSource = dr;
DropDownList1.DataTextField = "name";
DropDownList1.DataValueField = "id";
DropDownList1.DataBind();
当您将数据源更改为dr
时,它将删除您当前的——选择---
项(如预期)
您需要在数据源
绑定后添加它
DropDownList1.Items.Insert(0, new ListItem("---- select ----", 0));
DropDownList1.SelectedIndex = 0;
您需要将DropdownList的属性设置为true。否则,数据绑定将清除现有值。尝试此操作
public void filldropdown()
{
MySqlConnection conn = new MySqlConnection(connectionString);
conn.Open();
string query = "select * from category";
MySqlCommand cmd = new MySqlCommand(query, conn);
MySqlDataAdapter da = new MySqlDataAdapter(cmd);
DataSet ds=new DataSet();
da.Fill(ds);
DropDownList DropDownList1 = new DropDownList();
DropDownList1.DataSource = ds;
DropDownList1.DataTextField = "name";
DropDownList1.DataValueField = "id";
DropDownList1.DataBind();
DropDownList1.Items.Insert(0,new ListItem("---select---", "null"));
conn.Close();
}
有很多方法可以将项添加到数据绑定下拉列表中,比如我使用的Insert指定插入的位置(在哪个位置)
您是否尝试过按照PatterMister的建议设置附加数据绑定项?很抱歉延迟接受答案,它说您无法在7分钟内接受答案
DropDownList1.Items.Insert(1, "-- Select --");