How to list items with an empty for RadComboBox

Question

I have one RadComboBox. I fill it with a function which returns for example {Stack, Over, Flow, StackOverFlow} When I click RadCombobox that items are listed.

And I want to give first place for empty element.

And I tried to do below:

var stack= GetItems(SiteId);
RadComboBox1.Items.Add(new RadComboBoxItem("", "0"));
RadComboBox1.DataSource = stack;  

RadComboBox1.DataTextField = "Name";
RadComboBox1.DataValueField = "Id";
RadComboBox1.DataBind();

RadComboBox1.AllowCustomText = false;

There is no change. Only {Stack, Over, Flow, StackOverFlow} are listed.

When I write below code

var stack= GetItems(SiteId);

RadComboBox1.DataSource = stack;  

RadComboBox1.DataTextField = "Name";
RadComboBox1.DataValueField = "Id";
RadComboBox1.DataBind();
RadComboBox1.Items.Add(new RadComboBoxItem("xyz", "0"));
RadComboBox1.AllowCustomText = false;

Only {Stack, Over, Flow, StackOverFlow, xyz} are listed.

But I dont get the result which I want.

And the design side is below.

<telerik:RadComboBox ID="RadComboBox1" runat="server" Width="120px" MarkFirstMatch="true" Filter="Contains"></telerik:RadComboBox>

How can I do?

I want to list { " " , "Stack", "Over", "Flow", "StackOverFlow"}

Answer 1

Using your first choice, add RadComboBox1.AppendDataBoundItems = true before you call DataBind(). This means it won't clear out the existing items before adding the items from the data bind. You will need to manually clear the items beforehand if necessary:

RadComboBox1.Items.Clear();
RadComboBox1.ClearSelection();