my url routing is not performing well:
global.asax:
<%@ Import Namespace="System.Web.Routing" %>
<script runat="server">
    void Application_Start(object sender, EventArgs e) 
    {
        // Code that runs on application startup
        RegisterCustomRoutes(RouteTable.Routes);
    }
    public static void RegisterCustomRoutes(RouteCollection routeCollection)
    {
        routeCollection.MapPageRoute("AllAuthorRoute","author/{letter}","~/AllAuthor.aspx?");
           
    }
index.aspx.cs :
 protected void DataList2_ItemCommand(object source, DataListCommandEventArgs e)
    {
        if (e.CommandName == "AuthorAZ")
        {
            Response.Redirect(GetRouteUrl("AllAuthorRoute", null) + e.CommandArgument.ToString());
        }
    }
But the problem is does not find right path and got error