How to use ASP.NET tag in a server control?

Question

I have a dropdown

 <div>
     <asp:DropDownList ID="RegistrationDropDownList" runat="server">
         <asp:ListItem Value="NULL">All records</asp:ListItem>
         <asp:ListItem Value="1">Submitted records</asp:ListItem>
         <asp:ListItem Value="0">Non-Submitted records</asp:ListItem>
     </asp:DropDownList>
 </div>

I want to Show/hide <asp:ListItem Value="NULL">All records</asp:ListItem> based on a session variable

So I tried like this

 <asp:DropDownList ID="RegistrationDropDownList" runat="server">
 <%if (Convert.ToInt32(Session["user_level"]) == 1){ %>
     <asp:ListItem Value="NULL">All records</asp:ListItem>
 <%}%>
     <asp:ListItem Value="1">Submitted records</asp:ListItem>
     <asp:ListItem Value="0">Non-Submitted records</asp:ListItem>
 </asp:DropDownList>

But I got an error

code blocks are not supported in this context

I understand I cant use code blocks on controls that have the runat="server" but removing it breaks my code behind logic.

How can I solve this problem ?

It sounds like that conditional should be in the code-behind instead of the control mark-up. Maybe in Page_Load you can check the conditional and remove the NULL value item from the DropDownList. (Or the inverse, check the opposite condition to add the NULL value.) — David
– David, Commented Jul 18, 2013 at 17:33
When you add a runat='server' to an HTML control you change the rendering and code blocks aren't supported inside. — Pal R
– Pal R, Commented Jul 18, 2013 at 17:36

Andrei · Accepted Answer · 2013-07-18 17:35:09Z

3

This should be done in code behind:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack && Convert.ToInt32(Session["user_level"]) == 1)
    {
        RegistrationDropDownList.Items.Insert(0, new ListItem("All records", "NULL"));
    }
}

answered Jul 18, 2013 at 17:35

Andrei

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2 Comments

jackncoke Over a year ago

Blah 2 minutes Good job

meda Over a year ago

Thanks that solved my problem, do you know why it defaults to the second listitem (Submitted records) after loadin

jackncoke · Accepted Answer · 2013-07-18 17:37:56Z

0

Add it in the code behind

if (Convert.ToInt32(Session["user_level"]) == 1)
            {
                ListItem newItem = new ListItem();
                newItem.Value = null;
                newItem.Text = "All record";
                DropDownList1.Items.Add(newItem);

            }

answered Jul 18, 2013 at 17:37

jackncoke

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Comments

McGarnagle · Accepted Answer · 2013-07-18 17:40:14Z

0

It's a shame that ListItem doesn't have a Visibility property that you could bind to. The best solution I can think of is to write a class that extends DropDownList; add a method that inserts the "All Records" item before rendering.

public class ExtendedList : DropDownList
{
    protected override void OnLoad(EventArgs e)
    {
        if (Convert.ToInt32(Session["user_level"]) == 1)
        {
            Items.Insert(0, new ListItem { Value = "NULL", Text = "All Records" });
        }
    }
}

edited Jul 18, 2013 at 17:40

answered Jul 18, 2013 at 17:33

McGarnagle

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1 Comment

Pal R Over a year ago

Items.Add will add as the last item, instead use Insert to add it to position 0

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