Question

Code Behind (C#):

protected void Page_Load(object sender, EventArgs e)
    {
        try
        {
            if (!Page.IsPostBack)
            {
                List<string> lst = new List<string>();

                lst.Add("1");
                lst.Add("2");

                dlSample.DataSource = lst;
                dlSample.DataBind();
            }
        }
        catch (Exception ex)
        {

            throw;
        }
    }

    protected void dlSample_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        try
        {
            if (e.Item.DataItem.ToString().Equals("1"))
                e.Item.DataItem = "one";
        }
        catch (Exception ex)
        {

            throw;
        }
    }

ASP:

<asp:DataList ID="dlSample" runat="server" OnItemDataBound="dlSample_ItemDataBound">
        <ItemTemplate>
            <asp:Label ID="lbl" runat="server" Text='<%# Eval("") %>'></asp:Label>
        </ItemTemplate>
        </asp:DataList>

I have used List on my code and inserting items on it. After that I have binded it programmatically and on my ItemDataBound event I have modified an item at run-time. I have problem on displaying the items on the DataList control. My question is how would I display it using the Eval data-binding expression on my ASP or is there any approach aside on Eval?

Thank you very much in advance.

Answer 1

At the time when dlSample_ItemDataBound method is called, the expressions in the ItemTemplate are already evaluated and, even the DataItem is changed, the effect won’t be reflected.

You can use the following code block.

<asp:Label ID="lbl" runat="server" 
         Text='<%# (string)Container.DataItem == "1" ? "one" : (string)Container.DataItem %>'
         >
</asp:Label>

You can remove the OnItemDataBound="dlSample_ItemDataBound", because won’t be used anymore.

As an alternative, if you still want to use this handler:

<asp:DataList ID="dlSample" runat="server" OnItemDataBound="dlSample_ItemDataBound">
     <ItemTemplate>
          <asp:Label ID="lbl" runat="server"></asp:Label>
      </ItemTemplate>
</asp:DataList>

protected void dlSample_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        //dataitem is supposed to be a string object, so you can cast it to string, no need to call ToString()
        var item = (string)e.Item.DataItem;

        // find the label with "lbl" ID, use e.Item as the Naming Container
        var lbl = (Label)e.Item.FindControl("lbl");
        if (item == "1")
           lbl.Text = "one";
        else
           lbl.Text = item;
    }

I always prefer the first way to do these things.