asp.net Method for Calculating Execution Time per Page

This article provides an example of how asp.net calculates the execution time of each page.Share it for your reference.Specific analysis is as follows:

The asp.net code here calculates the execution time of each page without modifying the page's code. This code adds execution time to all pages.

public class PerformanceMonitorModule : IHttpModule
{
 public void Init(HttpApplication context)
 {
  context.PreRequestHandlerExecute += delegate(object sender,EventArgs e)
  {
   //Set Page Timer Star
   HttpContext requestContext = ((HttpApplication)sender).Context;
   Stopwatch timer = new Stopwatch();
   requestContext.Items["Timer"] = timer;
   timer.Start();
   };
  context.PostRequestHandlerExecute += delegate(object sender, EventArgs e)
  {
   HttpContext httpContext = ((HttpApplication)sender).Context;
   HttpResponse response = httpContext.Response;
   Stopwatch timer = (Stopwatch)httpContext.Items["Timer"];
   timer.Stop();
   // Don't interfere with non-HTML responses
   if (response.ContentType == "text/html")
   {
    double seconds = (double)timer.ElapsedTicks / Stopwatch.Frequency;
    string result_time = string.Format("{0:F4} sec ", seconds);
    RenderQueriesToResponse(response,result_time);
   }
  };
 }
 void RenderQueriesToResponse(HttpResponse response, string result_time)
 {
  response.Write("<div style=\"margin: 5px; background-color: #FFFF00\"");
  response.Write(string.Format("<b>Page Generated in "+ result_time));
  response.Write("</div>");
 }
 public void Dispose() { /* Not needed */ }
}

I hope that the description in this paper will be helpful to everyone's asp.net program design.