Clean page redirect for setting redirect inside logical code

Introduction

This article will detail how you can use the OnPreRender event to redirect a page from inside a logical set of code without getting the 'Thread was being aborted' error.

We start with the code in its error producing state. We are trying to redirect a page before all the code in the page is finished running, causing a thread abort on the page.

try
{
  if(obj != null)
  {
    //do some code

    //throws a 'Thread being aborted error' 
    //because a redirect is being done here
    Response.Redirect("Subscribers.aspx"); 
  }
  else
  {
    //some other code
  }
}
catch(Exception ex)
{
  //exception handling code
}

So to fix this we need to build a base page to inherit from and use the OnPreRender event to actually perform redirects before the page reloads completely, keeping threads from previous server processing from being aborted. We also create a handy page method SetPageRedirect that adds the URL to be redirected to to the session for access on the OnPreRender event.

public class GlobalPage 
{
  protected override void OnPreRender(EventArgs e)
  {
    if(Session[AppConst.PAGE_REDIRECT]!=null)
    {
      string redirectPage = Session["PAGE_REDIRECT"].ToString();
      Session["PAGE_REDIRECT"] = null;
      Response.Redirect(redirectPage);
    }

    base.OnPreRender (e);
  }

  /// <summary>
  /// Sets the redirect session variable for redirection on page render
  /// </summary>
  /// <param name="path"></param>
  public void SetPageRedirect(bool addRootPath, string path)
  {
    if(!path.StartsWith("/") && addRootPath)
      path = RootPath + "/" + path;
    else if (addRootPath)
      path = RootPath + path;
    Session[AppConst.PAGE_REDIRECT] = path;
}

So now we can inherit from this new page and use the functions to avoid getting any error:

try
{
  if(obj != null)
  {
    //do some code

    //no error throw because the redirect is being done 
    //in the OnPreRender event 
    this.SetPageRedirect(false,"RequestAccess.aspx");
  }
  else
  {
    //some other code
  }
}
catch(Exception ex)
{
  //exception handling code
}

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