I have a DropDownList
that is associated with a DataSource
in the aspx page. I need to add one more item when the page is loaded.
My Code:
<asp:LabelDropDownList ID="ddlVisualTemplate" runat="server" LabelText="Visual Template:" DataSourceID="VisualTemplateDataSource" DataTextField="Name" DataValueField="Id" AutoPostBack="true" OnSelectedIndexChanged="ddlVisualTemplate_SelectedIndexChanged"/>
<asp:EntityDataSource ID="VisualTemplateDataSource" runat="server"
ConnectionString="name=Entities"
DefaultContainerName="Entities" EnableFlattening="False"
EntitySetName="tbEmailVisualTemplates">
And I am trying to an extra item to it:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ddlVisualTemplate.Items.Add(new ListItem("None", string.Empty));
}
}
If I debug the code, it goes through it. But When the page is displayed dropdown doesn't contain "None"
.
It's most probably because you're adding the item before the DataBind()
. If you want to add an item with
ddlVisualTemplate.Items.Add()
then you have to do it after the dropdown is being bound.
If you look at http://msdn.microsoft.com/en-us/library/ms178472.aspx then DataBind is being done in PreRenderComplete. So you have to add the element in some event that occurs after PreRenderComplete.
Or you could do it on the ddlVisualTemplate.DataBound
event.
Probably too late for the original poster, but maybe useful for other users:
You can add the value "None", "Choose value", etc. in the designer (or in the code) and prevent DataBind
from overwriting it, by setting AppendDataBoundItems="true"
. This will make DataBind
append rather than clear.
For an example see Scott Guthrie's post ListControl.AppendDataBoundItems Property in ASP.NET 2.0.