Detecting Ajax Requests In ASP.NET MVC 5

Security is one of my major concerns nowadays and it is quite common that someone will try to browse to a particular URL given any chance. To avoid this, we can detect whether the request came from an Ajax request or from a normal browser request.

Within ASP.NET MVC5 applications is quite easy to check if a request is being made via AJAX through the extension named IsAjaxRequest() method that is available on the Request object. The IsAjaxRequest() actually works by simply performing a check for the X-Requested-With header.

The example below will show you how wrap this functionality inside an Action Filter so you can add this feature to any controller you want to perform this check upon.

Creating the Action Filter:

	// Copyright (c) 2018, Jordi Corbilla
	// All rights reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// - Redistributions of source code must retain the above copyright notice,
	// this list of conditions and the following disclaimer.
	// - Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	// - Neither the name of this library nor the names of its contributors may be
	// used to endorse or promote products derived from this software without
	// specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
	// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	// POSSIBILITY OF SUCH DAMAGE.
	using System;
	using System.Reflection;
	using System.Web.Mvc;
	namespace easyTimeSheets.MVC
	{
	[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
	public sealed class AjaxOnlyAttribute : ActionMethodSelectorAttribute
	{
	public override bool IsValidForRequest(ControllerContext controllerContext, MethodInfo methodInfo)
	{
	if (controllerContext == null)
	throw new ArgumentNullException(nameof(controllerContext));
	return controllerContext.RequestContext.HttpContext.Request.IsAjaxRequest();
	}
	}
	}

view raw AjaxOnlyAttribute.cs hosted with ❤ by GitHub

Then just use the attribute in any of the actions you want to perform this operation:

	// Copyright (c) 2018, Jordi Corbilla
	// All rights reserved.
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// - Redistributions of source code must retain the above copyright notice,
	// this list of conditions and the following disclaimer.
	// - Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	// - Neither the name of this library nor the names of its contributors may be
	// used to endorse or promote products derived from this software without
	// specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
	// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	// POSSIBILITY OF SUCH DAMAGE.
	public class HomeController : Controller
	{
	[AjaxOnly]
	public ActionResult Detail()
	{
	return View();
	}
	}

view raw HomeController.cs hosted with ❤ by GitHub

And now, if you try to browse that action from a normal request you will get the following error:

Now you can make your site more secure without worrying about someone inadvertently clicking to  the action.