如何在填充的下拉列表中包括所选值

Question

I am using linq to fetch from database to populate in drop down list in asp.net using below code:

XXXDataContext summary = new XXXDataContext();
protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
      var binmy = ( from bin in summary SUBPRODUCTs
                    order by bin.SUBID
                    select new { bin.SUBID, bin.SUBValue }
                  );                      
      dropdownsummary.DataValueField = "SUBID";
      dropdownsummary.DataTextField = "SUBValue";
      dropdownsummary.DataSource = binmy;
      DataBind();
   }
}

Here I want to include 'All' as default value how to do that?

Answer 1

Add this item in the html dropdown declaration and set the 'AppendDataBoundItems' property to true. See below...

<asp:DropDownList ID="dropdownsummary" runat="server" AppendDataBoundItems="true">
    <asp:ListItem Selected="True" Value="-1" Text="All"></asp:ListItem>
</asp:DropDownList>

Answer 2

Use:

dropdownsummary.DataBind();  

Instead of :

DataBind();  

Answer 3

Try This

dropdownsummary.DataValueField = "SUBID";
dropdownsummary.DataTextField = "SUBValue";
dropdownsummary.DataSource = binmy;
dropdownsummary.Items.Insert("0", new ListItem ( "All" , "0" ));