How to stay in the same page if paging in gridview on clicking back button using C#

I have a GridView on ASP.NET web form which I have bound to a data source and set it to have 10 records per page.

I also have a hyper link column on the GridView, such that a user can navigate to another page (details page) 
from the list. On the details page, they have "Back" button to return to the GridView page

I tried the below code but its not working
  
     <pre lang="c#">protected void GridViewIndexChanging(object sender, GridViewPageEventArgs e)
    {
        myGridView.PageIndex = e.NewPageIndex;
        Session["pageNumber"] = e.NewPageIndex;
    }
        if (!IsPostBack)
        {
            if (Session["pageNumber"] != null)
            {
                GridViewIndexChanged(myGridView, new GridViewPageEventArgs((int)Session["pageNumber"]));
            }
        }

I tried the above code but its not working