using System;namespace System.Web.Mvc{ ???/// <summary>Represents a class that extends the <see cref="T:System.Web.HttpRequestBase" /> class by adding the ability to determine whether an HTTP request is an AJAX request.</summary> ???public static class AjaxRequestExtensions ???{ ???????/// <summary>Determines whether the specified HTTP request is an AJAX request.</summary> ???????/// <returns>true if the specified HTTP request is an AJAX request; otherwise, false.</returns> ???????/// <param name="request">The HTTP request.</param> ???????/// <exception cref="T:System.ArgumentNullException">The <paramref name="request" /> parameter is null (Nothing in Visual Basic).</exception> ???????public static bool IsAjaxRequest(this HttpRequestBase request) ???????{ ???????????if (request == null) ???????????{ ???????????????throw new ArgumentNullException("request"); ???????????} ???????????return request["X-Requested-With"] == "XMLHttpRequest" || (request.Headers != null && request.Headers["X-Requested-With"] == "XMLHttpRequest"); ???????} ???}}一直不清楚服务端是如何判断一个请求是否是ajax请求，通过ILSpy查看，才得知是通过判断请求头是否存在
X-Requested-With:XMLHttpRequest 来判断是否是ajax请求。
通过http上下文判断是否是Ajax请求
原文地址：https://www.cnblogs.com/tangchun/p/9121334.html