如何从asp.net中的label.text调用函数背后的代码

Question

I am trying to call a function defined in code behind from Label.Text but it's not working. Here is the code... code in .aspx file

<asp:Label runat="server" Text='<%# GetPagingCaptionString() %>' ID="pagenumberLabel"></asp:Label>

code block from code behind

public string GetPagingCaptionString()
        {
            int currentPageNumber = Convert.ToInt32(txtHidden.Value);
            int searchOrderIndex;
            if (int.TryParse(Convert.ToString(Session["searchOrderIndex"]), out searchOrderIndex))
            {
                return string.Format("{0} to {1} orders out of {2}", (currentPageNumber * 20) + 1,
                    (currentPageNumber + 1) + 20, GetItemsCount(searchOrderIndex.ToString()));
            }
            return String.Empty;
        }

Can anyone tell me what's wrong here.

Answer 1

Unless you're using a template based control (such as <asp:Repeater> or <asp:GridView> ) then you can't use inline code-blocks such as you have within a server-side control.

In other words, you can't have <%=%> blocks within the attributes of server-side controls (such as <asp:Label> ). The code will not be run and you will find the code is actually sent as part of the rendered HTML. The exception is for databinding controls where <%#%> code-blocks are allowed.

You're better off in this situation setting the .Text property in the code-behind itself.

For instance in your page-load function....

protected void Page_Load(object sender, EventArgs e)
{
  if (!Page.IsPostBack)
  {
    pagenumberLabel.Text = GetPagingCaptionString();
  }
}

Answer 2

If you add a Property to your page it will be accessible from your aspx like so:

<asp:Label runat="server" Text='<%= PagingCaptionString %>' ID="pagenumberLabel" />

NB <%= %> tag rather than <%# %> which is used for databinding controls

Codebehind:

public string PagingCaptionString {
    get {
        int currentPageNumber = Convert.ToInt32(txtHidden.Value);
        int searchOrderIndex;
        if (int.TryParse(Convert.ToString(Session["searchOrderIndex"]), out searchOrderIndex))
        {
            return string.Format("{0} to {1} orders out of {2}", (currentPageNumber * 20) + 1,
                (currentPageNumber + 1) + 20, GetItemsCount(searchOrderIndex.ToString()));
        }
        return String.Empty;
    };
}