Telerik Radcombobox.SelectedValue not working

Question

I am trying to populate my telerik dropdown on page load. I am using the following code for this:

ddIntervention.SelectedValue=3

The RadComboBox is inside two update panels.

aspx page:

<telerik:RadComboBox ID="ddIntervention" runat="server" DataSourceID="SqlDataSource3" 
 DataTextField="ProcedureDesc" MaxHeight="180px" Filter="Contains" 
 DataValueField="ProcedureID" HighlightTemplatedItems="True" MarkFirstMatch="True" 
 Width="350px" EmptyMessage="Search By Intervention Name" EnableAutomaticLoadOnDemand="True" 
 ShowMoreResultsBox="True" EnableVirtualScrolling="True" ItemsPerRequest="10" 
 DropDownWidth="350px" AutoPostBack="True" CausesValidation="False" 
 ResolvedRenderMode="Classic"  AllowCustomText="true">
</telerik:RadComboBox>


<asp:SqlDataSource ID="SqlDataSource3" runat="server" 
 ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
 SelectCommand="SELECT [ProcedureID], [ProcedureDesc], [DateDeleted] FROM 
 [Vw_UploadRef_Procedures] WHERE ([DateDeleted] IS NULL)
</asp:SqlDataSource>

Answer 1

I think your problem will be EnableAutomaticLoadOnDemand="True" reason because the RadComboBox will be empty until you click on it. That's why you set SelectedValue won't take effect on Page_Load

Update Code

.aspx

<asp:ScriptManager ID="sm" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="up" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <asp:Button ID="btn" runat="server" Text="Dummy Button" />
        <br /><br />
        <asp:UpdatePanel ID="up1" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
                <telerik:RadComboBox ID="rcb" runat="server" AutoPostBack="true" 
                    AllowCustomText="true" HighlightTemplatedItems="true"
                    EmptyMessage="Search By Name" MarkFirstMatch="true"
                    ShowMoreResultsBox="true" EnableVirtualScrolling="true"
                    DropDownWidth="350px" CausesValidation="false"
                    ItemsPerRequest="10" RenderMode="Classic"
                    OnSelectedIndexChanged="rcb_SelectedIndexChanged"></telerik:RadComboBox>
                <br />
                <asp:Label ID="lbl" runat="server"></asp:Label>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="rcb" />
            </Triggers>
        </asp:UpdatePanel>
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="btn" />
    </Triggers>
</asp:UpdatePanel>

.cs

protected void Page_Load(object sender, EventArgs e)
{
    // Check
    if (!IsPostBack)
    {
        // Variable
        string[] text = { "A","B","C", "D", "E", "F" };
        DataTable dt = new DataTable();
        dt.Columns.Add("Text");
        dt.Columns.Add("Value");

        // Add Rows
        for (int i = 0; i < text.Length; i++)
            dt.Rows.Add(text[i], i + "");

        // Bind to Drop Down
        rcb.DataSource = dt;
        rcb.DataTextField = "Text";
        rcb.DataValueField = "Value";
        rcb.DataBind();

        // Check
        if (rcb.Items.Count > 0)
        {
            rcb.SelectedValue = "3";
            rcb_SelectedIndexChanged(rcb, new RadComboBoxSelectedIndexChangedEventArgs
            (rcb.SelectedItem.Text.Trim(), "", rcb.SelectedValue, "")); 
            // Trigger Selected Index Changed
        }
    }
}

protected void rcb_SelectedIndexChanged(object sender, RadComboBoxSelectedIndexChangedEventArgs e)
{
    // Check if the dropdown is selectedIndex is greater or equal first item
    // if you have "Please select" on first item just change ">=" to ">"
    if (rcb.SelectedIndex >= 0)
    {
        lbl.Text = rcb.SelectedItem.Text.Trim();
    }
}

Result On Page Load