How to use Url Rewriting in asp.net

Question

I am working on an asp.net application where I am using Url Rewriting. My webpage name is NewsDetail.aspx whose Code is:

<asp:Content ContentPlaceHolderID="ContentPlaceHolder1" ID="Content1" runat="server">
  <div style="min-height: 150px; padding: 10px 10px;">
    <marquee behavior="scroll" direction="up" scrollamount="2" height="150">
        <asp:ListView ID="listNews" runat="server">
           <ItemTemplate>
               <p>
                <a href="NewsDetail.aspx?ID=<%#Eval("ID") %>"> <%#Eval("Title") %> </a>
               </p>
             </ItemTemplate>
        </asp:ListView>
     </marquee>
  </div>
</asp:Content>

I have Bind This Listview in Default.aspx WebPage Page-Load Event as:

DataTable dt = new DataTable();
            dt = new Process_News().SelectPublishNews();
            if (dt.Rows.Count > 0)
            {
                listNews.DataSource = dt;
                listNews.DataBind();
            }

I want that when user clicks on an item in "listNews" Listview then it should be Redirected to NewsDetail.aspx WebPage.If user Click on item whose ID=1 Then the Addressbar is showing

http://AtharvaJournal.com/NewsDetail.aspx?ID=1

But I want to show as http://AtharvaJournal.com/News/1

For this i have done following code in global.asax file:

void RegisterRoutes(RouteCollection routes)
    {        
        routes.MapPageRoute("News", "News/{Id}", "~/NewsDetail.aspx");
    }

    protected void Application_Start(object sender, EventArgs e)
    {
        RegisterRoutes(RouteTable.Routes);
    }

In NewsDetail.aspx Page I have done following Code:

if (!string.IsNullOrEmpty(Page.RouteData.Values["Id"].ToString()))
{
     string id = Page.RouteData.Values["Id"].ToString();

     long ID = Convert.ToInt64(Page.RouteData.Values["Id"].ToString());
     dt = new Process_News().SelectByID(ID);
     if (dt.Rows.Count > 0)
     {
         hTitle.InnerText = dt.Rows[0]["Title"].ToString();
         PDetail.InnerText = Server.HtmlDecode(dt.Rows[0]["Contents"].ToString());                      

     }

 }

Now when I write following thins in my addressbar : ( http://AtharvaJournal.com/News/1) Then It runs well,But when i directly click on any item in "listNews" ListView Then It shows the exception as:-

"Object reference not set to an instance of an object"

Please Help me Here.

Answer 1

You have two problems:

First, your (second) url does not use the routing table, change the url to http://AtharvaJournal.com/News/THE_ID there too.

Or use this to get the Id for the url without url mapping:

Request.QueryString["Id"]

Second, you are checking Page.RouteData.Values["Id"].ToString() while Page.RouteData.Values["Id"] is null.

Try this instead:

(string)Page.RouteData.Values["Id"]

Answer 2

I Found a better way to solve this problem. In ListView named "listnews" following code was written inside itemtemplate:-

<a href="NewsDetail.aspx?ID=<%#Eval("ID") %>"> <%#Eval("Title") %> </a>

I modified it as

<a href="News/<%#Eval("ID") %>"> <%#Eval("Title") %> </a>

Now it is working well and good for me.