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ASP.NET Advanced Generic Handler ASHX

, 2 Apr 2012 CPOL
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Take your Generic Handlers to the next level...
This is an old version of the currently published article.


In ASP.NET, we have something that is usually overlooked that is called Generic Handlers. I see a lot o f people using pages to process AJAX requests when we can use this much less expensive endpoint. This is an completely worked out Generic Handler that truly knows how to handle your http (AJAX and not) requests.


For a long time I used plain Generic Handlers (ASHX files) to handle my AJAX requests but it felt stupid and painful. I mean, the functionality was there but the whole process of handling the requests wasn't straight forward. So I made a list of the things I would like to have on and handler:

  • NEW! Support for complex objects as method argument
    • Now you can put your custom classes on the handler methods arguments.
    • Automatically hydrates the class and all its nested types!!
  • Standard way to parse the query string
  • Transparently handle multiple methods within the same handler
  • Support methods with multiple typed arguments, not just strings
  • Support Methods that receive lists as an argument
  • Support passing less arguments than the method is expecting (like optional parameters)
  • Transparently reply either POSTs or GETs
  • Support default object serialization to JSON but still let me override it on each method
  • Return application/json by default but still let me override it on each method
  • Support jQuery $.ajax request
  • Support request by query string (URL right on the browser)
  • A way to visualize the methods the handler supports (like webservices do)
  • Extensible
And that's it... I can tell you in advance that it already does all this and maybe more.

Using the code

List the Handler methods

I've provided a very basic way of listing the methods the Handler exposes. This is specially useful to test if the handler is working correctly (like on webservices). Do do so just append ?help at the end of the handler URL:


Calling the Handler from the browser URL

Using this handles is very simple:

  1. Create a new Generic Handler
  2. Clear everything inside the handler class
  3. Inherit from my Handler class
  4. DONE! Now you only need to add your methods.

Let's create a very simple example that receives a name and returns a string (see on the project).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using App.Utilities.Web.Handlers;

namespace CodeProject.GenericHandler
	public class MyFirstHandler : BaseHandler
		// I don't bother specifying the return type, it'll be serialized anyway
		public object GreetMe(string name) 
			return string.Format("Hello {0}!", name);

To call this method through a URL use:


AJAX Request using jQuery

If you want to use jQuery AJAX method you just need to know the object the handler is expecting to get. On the data property of the $.ajax request you must pass something like:

{ method: 'The method you want to call', args: { the arguments to pass } }
Be aware that everything is case sensitive!
	url: 'MyFirstHandler.ashx',
	type: 'GET',
	data: { method: 'GreetMe', args: { name: 'AlexCode'} },
	success: function (data) {

Writing a method that returns HTML

Like I said on my intention points above, I need to have some methods that return whatever I want like HTML, XML, images, files, etc... The default behavior of the handler is to return JSON so, by method, we need to explicitly say that we want to handle things our way. For that just use these lines anywhere within the method:

SkipContentTypeEvaluation = true;	
SkipDefaultSerialization = true;

// you can specify the response content type as follows
context.Response.ContentType = "text/html";
Lets see an example on how we could write a method on the handler that returns HTML:
public object GiveMeSomeHTML(string text)
	StringBuilder sb = new StringBuilder();
	sb.Append("<head><title>My Handler!</title></head>");
This is a HTML page returned from the Handler
The text passed was: " + text + "

	context.Response.ContentType = "text/html";
	SkipContentTypeEvaluation = true;
	SkipDefaultSerialization = true;

	return sb.ToString();

Optional Parameters and nullable types

All parameters in the methods are optional. If they're not passed their default value is assigned. Also all parameters can be nullable. In this case the default value will be null.

Support for complex types

Say you have a JSON object and a class server side that maps it. Hydrating this class server side is a pain. Usually we pass each property as an argument of the method on the Handler, instantiate a new instance of the class and set the properties one by on... a pain right? NO MORE! This handler now supports automatic class instance creation and property set. Something I like to call Object Hydratation! :) And there's more! If this class have properties that also expose other custom classes they will be hydrated too!! Just make sure all classes have a public default constructorr

// Now you can have method like this
public object SendPersonData(Person person)
return person.Name;

// your ajax call object would be something like
data: { 
     method: 'SendPersonData', 
          person: { Name: 'Alex' } 

Please have a look at the attached code sample for more examples.

Points of Interest

I can say that this handler already saved me a good amount of development and maintenance hours. Currently all my AJAX requests point to a method on an handler like this.

History ;

  • v1.1 - Added support for complex arguments
  • v1.0 - The first wide open version 
  • This is a work in progress, I keep improving it regularly.

I have no doubt that you'll try to use this in scenarios I haven't predicted. Please send me your requests and desires, I'll do my best to implement them.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Switzerland Switzerland
Senior IT Consultant working in Switzerland as Senior Software Engineer.

Find more at on my blog.

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Comments and Discussions

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QuestioncURL query? Pin
bradut18-Oct-15 18:35
memberbradut18-Oct-15 18:35 
AnswerRe: cURL query? Pin
AlexCode19-Oct-15 5:49
professionalAlexCode19-Oct-15 5:49 
GeneralRe: cURL query? Pin
bradut19-Oct-15 9:41
memberbradut19-Oct-15 9:41 
GeneralRe: cURL query? Pin
AlexCode19-Oct-15 22:30
professionalAlexCode19-Oct-15 22:30 
GeneralRe: cURL query? Pin
bradut20-Oct-15 6:39
memberbradut20-Oct-15 6:39 
GeneralRe: cURL query? Pin
AlexCode20-Oct-15 9:01
professionalAlexCode20-Oct-15 9:01 
Questionjson array to generic handler Pin
snow_cap3-Jul-14 11:13
membersnow_cap3-Jul-14 11:13 
AnswerRe: json array to generic handler Pin
AlexCode4-Jul-14 2:59
professionalAlexCode4-Jul-14 2:59 
GeneralMy vote of 1 Pin
Member 1043844613-Feb-14 0:57
memberMember 1043844613-Feb-14 0:57 
GeneralRe: My vote of 1 Pin
AlexCode13-Feb-14 22:56
professionalAlexCode13-Feb-14 22:56 
GeneralRe: My vote of 1 Pin
Member 1043844613-Feb-14 23:39
memberMember 1043844613-Feb-14 23:39 
GeneralRe: My vote of 1 Pin
AlexCode16-Feb-14 21:51
professionalAlexCode16-Feb-14 21:51 
GeneralMy vote of 1 Pin
Matty2213-Jun-13 21:06
memberMatty2213-Jun-13 21:06 
GeneralRe: My vote of 1 Pin
AlexCode13-Jun-13 21:25
professionalAlexCode13-Jun-13 21:25 
GeneralRe: My vote of 1 Pin
AbsCode4-Aug-13 1:47
memberAbsCode4-Aug-13 1:47 
GeneralMy vote of 4 Pin
Sniper909-Jun-13 23:09
memberSniper909-Jun-13 23:09 
QuestionJson.NET? Pin
ahagel28-May-13 18:24
memberahagel28-May-13 18:24 
AnswerRe: Json.NET? Pin
AlexCode28-May-13 22:15
professionalAlexCode28-May-13 22:15 
GeneralMy vote of 1 Pin
abforce27-May-13 10:39
memberabforce27-May-13 10:39 
GeneralRe: My vote of 1 Pin
AlexCode27-May-13 10:52
professionalAlexCode27-May-13 10:52 
GeneralRe: My vote of 1 Pin
abforce28-May-13 6:00
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GeneralRe: My vote of 1 Pin
AlexCode28-May-13 7:05
professionalAlexCode28-May-13 7:05 
GeneralRe: My vote of 1 Pin
HaBiX29-May-13 7:59
memberHaBiX29-May-13 7:59 
GeneralRe: My vote of 1 Pin
AlexCode29-May-13 20:47
professionalAlexCode29-May-13 20:47 
GeneralRe: My vote of 1 Pin
HaBiX29-May-13 21:46
memberHaBiX29-May-13 21:46 
GeneralRe: My vote of 1 Pin
AlexCode29-May-13 23:40
professionalAlexCode29-May-13 23:40 
GeneralRe: My vote of 1 Pin
HaBiX29-May-13 23:53
memberHaBiX29-May-13 23:53 
GeneralMy vote of 5 Pin
Prasad Khandekar27-May-13 8:18
professionalPrasad Khandekar27-May-13 8:18 
GeneralRe: My vote of 5 Pin
AlexCode27-May-13 9:08
professionalAlexCode27-May-13 9:08 
QuestionMy vote of 5 Pin
Alireza_136221-Apr-13 23:44
memberAlireza_136221-Apr-13 23:44 
AnswerRe: My vote of 5 Pin
AlexCode22-Apr-13 0:28
memberAlexCode22-Apr-13 0:28 
GeneralRe: My vote of 5 Pin
Alireza_136222-Apr-13 22:44
memberAlireza_136222-Apr-13 22:44 
QuestionArray hydration Pin
fvilli3-Apr-13 4:29
memberfvilli3-Apr-13 4:29 
AnswerRe: Array hydration Pin
AlexCode3-Apr-13 20:22
memberAlexCode3-Apr-13 20:22 
AnswerRe: Array hydration Pin
fvilli3-Apr-13 21:51
memberfvilli3-Apr-13 21:51 
GeneralRe: Array hydration Pin
AlexCode4-Apr-13 20:04
memberAlexCode4-Apr-13 20:04 
GeneralRe: Array hydration Pin
kshicha9-Apr-13 5:35
memberkshicha9-Apr-13 5:35 
GeneralRe: Array hydration Pin
AlexCode11-Apr-13 5:08
memberAlexCode11-Apr-13 5:08 
GeneralRe: Array hydration Pin
kshicha15-Apr-13 1:53
memberkshicha15-Apr-13 1:53 
QuestionMy vote of 5 Pin
Ofiros36517-Feb-13 4:19
memberOfiros36517-Feb-13 4:19 
QuestionDefault content type Pin
Member 93042114-Feb-13 4:15
memberMember 93042114-Feb-13 4:15 
AnswerRe: Default content type Pin
AlexCode18-Feb-13 11:24
memberAlexCode18-Feb-13 11:24 
GeneralMy vote of 5 Pin
spkichara3-Aug-12 20:51
memberspkichara3-Aug-12 20:51 
GeneralRe: My vote of 5 Pin
AlexCode15-Aug-12 21:22
memberAlexCode15-Aug-12 21:22 
QuestionHow about cookies? Pin
Corgalore17-Jul-12 8:45
memberCorgalore17-Jul-12 8:45 
AnswerRe: How about cookies? Pin
AlexCode17-Jul-12 11:08
memberAlexCode17-Jul-12 11:08 
QuestionHow about turning off cache? Pin
Cherepoc19-Jun-12 3:08
memberCherepoc19-Jun-12 3:08 
AnswerRe: How about turning off cache? Pin
AlexCode19-Jun-12 9:56
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GeneralRe: How about turning off cache? Pin
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GeneralRe: How about turning off cache? Pin
AlexCode20-Jun-12 4:21
memberAlexCode20-Jun-12 4:21 

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