show popup with text without redirecting

Hi , I am using sharepoint 2013 asp HyperLink control .  See my code below,

Here if part working perfectly.

How to show the same pop up box without url in else block.

For Example i want to show "No item found" in popup

if (ViewState["Share"] != null)
            {
                string url= "https://www.google.co.in"                
                HyperLink1.NavigateUrl = "javascript:SP.UI.ModalDialog.ShowPopupDialog('" + url + "')";
            }
  else
            {
                         // what code here

            }

Thanks in advance