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ASP .Net MapRequestHandler slow

We have rolled out a classic ASP.Net WebService application with large traffic. Though our database is running quite well (<10 ms response times), most of the time spent in WebServer is in the MapRequestHandler stage.
The issue seems to be deep in the ASP .Net stack and without any information available on net, I am clueless as to how to go about improving it.
We use XML payloads for request/response (if that would help in providing a solution).

Please post you handler code and your config files.
MapRequestHandler - The MapRequestHandler event is used by the ASP.NET infrastructure to determine
request handler for the current request based on the file-name extension of the requested resource. MapRequestHandler is an event that the handlers need to implement, I suspect its stuck at some delegate that maps some custom file.
I suspect its 1) Not finding, looping around to find that custom file handler, you may not 2) using the async handler
You have to chase down the various delegate that use this event and setup a break point
Make sure they are Async & Registered for e.g.
<add verb="*" path="*.aspx" type="System.Web.UI.PageHandlerFactory" />
<add verb="*" path="*.config" type="System.Web.HttpForbiddenHandler" />
<add verb="*" path="*.asmx" type="System.Web.Services.Protocols.WebServiceHandlerFactory" />
Then under the handlers verify
<httpHandlers>
<add verb="*" path="*.MyCustomaspx" type="MyCustomHTTPhandler"/>
</httpHandlers>
In your implementation use the async version base handler
// dervie from Async HttpTaskAsyncHandler
public class MyCustomHTTPhandler: HttpTaskAsyncHandler {
public override Task ProcessRequestAsync(HttpContext context)
{
//throw new NotImplementedException();
//blah blah.. some code
}
}
Last resort, not recommended - from SO here, if your handler/page doesnt modify session variables, you can skip the session lock.
<% #Page EnableSessionState="ReadOnly" %>
If your page does not read any session variables, you can opt out of this lock entirely, for that page.
<% #Page EnableSessionState="False" %>
If none of your pages use session variables, just turn off session state in the web.config.
<sessionState mode="Off" />
Based on this if you want to customize session state just based on your specific page/handler
using System;
using System.Web;
public class CustomSessionStateModule : IHttpModule
{
public void Dispose(){ //.. }
public void Init(HttpApplication context){
context.BeginRequest += new EventHandler(context_BeginRequest);
}
void context_BeginRequest(object sender, EventArgs e){
HttpContext currentContext = (sender as HttpApplication).Context;
// here you can filter and turn off/on the session state
if (!currentContext.Request.Url.ToString().Contains("My Custom Handler or Page Value")){
// for e.g. change it to read only
currentContext.SetSessionStateBehavior(
System.Web.SessionState.SessionStateBehavior.ReadOnly);
}
else {
//set it back to default
currentContext.SetSessionStateBehavior(
System.Web.SessionState.SessionStateBehavior.Default);
}
}
}

Dynamic use of cookies in Forms-Authentication

Currently I have 2 ways:
when i set my web.config cookieless="UseCookies" my url looks that:
http://example.com/Stuff
<sessionState timeout="60" cookieless="UseCookies"/>
when i set cookieless="true" i have such urls
http://example.com/%28S%28uanyuxwgaviyonky0lxwq3vq%29%29/Stuff
<sessionState timeout="60" cookieless="true"/>
Is i possible to set cookieless property dynamic? Something like
if(/*condition*/)
{
sessionState .cookieless = "true";
}
else
{
sessionState .cookieless = "UseCookies";
}
This must be somewhere in SessionStart of Global.asax or something

The basic Idea here is you want to modify the WebConfig file at runtime. i didn't tried my-self , but as curiosity i searched over internet , and found This link
and according to this your code in Global.asax will be like
Note : this actually writes the new value the web.config
void Application_Start(object sender, EventArgs e)
{
// Code that runs on application startup
Configuration config;
config = WebConfigurationManager.OpenWebConfiguration("~");
SessionStateSection SessionState = config.GetSection("system.web/sessionState") as SessionStateSection;
if (SessionState != null)
{
SessionState.Mode = System.Web.SessionState.SessionStateMode.InProc;// changes
if (true/*condition*/)
{
SessionState.Cookieless = System.Web.HttpCookieMode.UseCookies;
}
else
{
SessionState.Cookieless = System.Web.HttpCookieMode.UseUri; // not sure about this one
}
config.Save();
}
}

This question is discussed regularly since 2003 (see for example Switch dynamically to cookieless session state asp.net?.
You cannot change cookieless false/true from the application because decision is made by IIS before begin_request fired.
Some available options are:
A.
<system.web>
<sessionState cookieless="AutoDetect"></sessionState>
</system.web>
B.
Set some folder inside your webroot as web application and set cookieless="true"

IIS manage it before application request start so you can not change it on application level.

How do I restrict POST access to a HttpHandler?

I have a few http handlers (IHttpHandler) in my asp.net web project. Now I want to restrict access to these handlers. For Handler1 I want to allow only POST requests, and for Handler2 I want to allow only GET requests.
In my web.config I modified the <httpHandlers> section as shown below, but both handlers still process all verb types. Is there something I've missed? I'm testing it using IIS Express.
<httpHandlers>
<add verb="POST" path="Handler1.ashx" type="MyNamesapce.Handler1, MyAssembly"/>
<add verb="GET" path="Handler2.ashx" type="MyNamesapce.Handler2, MyAssembly"/>
</httpHandlers>

The reason this isn't working for you is that you've conflated two slightly different "flavours" of something that implements IHttpHandler.
There are two ways that you can implement an IHttpHandler with asp.net:
Create a class that implements IHttpHandler, e.g. MyCustomHandler.cs. This type of handler won't respond to any requests without being configured in your web.config file.
Create an .ashx file (which it looks like you've done), e.g. MyOtherHandler.ashx. This type of handler will respond to any requests to its URL, e.g. http://localhost/MyOtherHandler.ashx
The first type requires entries in the web.config file to work, the second doesn't. This is why you're seeing your .ashx handlers responding to all HTTP verbs, because they're being handled by the part of the asp.net framework that responds to requests for .ashx files, rather than being triggered by your web.config file. If you're using IIS Express, you can see this configured in the file %USERPROFILE%\Documents\IISExpress\config\applicationhost.config. Search for ".ashx" and you'll find a line similar to the below in the <system.webServer><handlers> section:
<add name="SimpleHandlerFactory-Integrated-4.0" path="*.ashx"
verb="GET,HEAD,POST,DEBUG" type="System.Web.UI.SimpleHandlerFactory"
preCondition="integratedMode,runtimeVersionv4.0" />
This is equivalent to what you've been adding to your web.config, but is responsible for telling IIS/asp.net "respond to any URLs that end in .ashx with any of the listed verbs by having the code in the type System.Web.UI.SimpleHandlerFactory deal with it. This code then loads your .ashx file.
To create a handler that can respond to any address you choose, you need (in short) a .cs file containing something similar to:
using System.Web;
namespace HttpHandlers
{
public class Handler4 : IHttpHandler
{
public bool IsReusable
{
get { return true; }
}
public void ProcessRequest(HttpContext context)
{
context.Response.Write("Hello World from Handler4.cs");
}
}
}
You can then wire it into your web.config file with:
<add name="Handler4" verb="POST" path="Handler4.ashx" type="HttpHandlers.Handler4, HttpHandlers" />
NOTE: My project that I created to test this is called "HttpHandlers", hence the type declaration that I've specified in that web.config snippet.

How to remove X-AspNetMvc-Version from header response without touching source code file (Global.asax.cs)?

I need to disable the X-AspNetMvc-Version from the response header of a large number of applications. The server where the applications are hosted has just the content and config files Global.asax, web.config, app.config for the application and source code files (*.cs) reside with some other team.
I could only find the solution as adding
MvcHandler.DisableMvcResponseHeader = true;
to Global.asax.cs.
Any alternative solution(s) that involves working with any config file(s)?

Set enableVersionHeader to false in your web.config is an alternate, I would prefer the web.config change to a handler solution like you have, obviously, since you will not need to access global.asax.cs to make the change:
just copy this line into the web.config’s <system.web> section:
<httpRuntime enableVersionHeader="false" />
http://msdn.microsoft.com/en-us/library/system.web.configuration.httpruntimesection.enableversionheader(v=vs.110).aspx
http://madskristensen.net/post/Remove-the-X-AspNet-Version-header

Unfortunately the only way is to use the following code in your Global.asax:
MvcHandler.DisableMvcResponseHeader = true;

This is an old post but no marked answer. I was able to achieve this using the code below. In your global.asax.cs we can remove any header.
protected void Application_PreSendRequestHeaders()
{
if (HttpContext.Current != null)
{
HttpContext.Current.Response.Headers.Remove("x-aspnet-version");
}
}

How to define endpoint without web.config or httpModule?

I would like to make a RESTful app of HTTPhandlers without having to define every endpoint by making an entry in the web.config, i'd like the style of attaching attributes to a class constructor eg:
public class obj : IHttpHandler
{
[WebGet(UriTemplate = "/accounts/{id}")]
public obj(string id)
{
// this is just an eg, it worild normally include caching and
// a template system
String html = File.ReadAllText("/accounts/accounts.htm");
html.replace("id", id);
httpcontext.current.response.write(html)
}
}
instead of
<httpHandlers>
<clear />
<add verb="GET" path="/accounts/*" type="MyApp.obj" />
</httphandlers>
The way i'm doing it now i have 100's of endpoints in the web.config :( i'd rather define them in the class. And i don't want to make extra files (.asmx) either. I'd like an app of just .htm files with tokens and .cs files
Thanks!

You could automate the registration of the endpoints and so on, with a custom ServiceHost, which overrides the ApplyConfiguration() method, which then virtualizes the configuration so that it does not have to be in the web.config file.
Here's a starting point. It doesn't do exactly what you want, but it illustrates the concept of virtualizing the configuration.