为什么Request.ContentType在我的请求中始终为空？

Question

我有一个基本控制器类，它试图查看Request.ContentType来查看它是一个json请求还是一个常规的HTML请求。基础控制器然后在基类上设置一个简单的枚举，并且适当的控制器返回正确的类型。但是，Request.ContentType始终是一个空字符串。这是为什么？

我的基本控制器：

namespace PAW.Controllers 
{ 
    public class BaseController : Controller 
    { 
     public ResponseFormat ResponseFormat { get; private set; } 
     public User CurrentUser { get; private set; } 

     protected override void OnActionExecuting(ActionExecutingContext filterContext) 
     { 
      base.OnActionExecuting(filterContext); 

      Culture.SetCulture(); 

      if (this.Request.ContentType.ToLower() == "application/json") 
       this.ResponseFormat = ResponseFormat.Json; 
      else 
       this.ResponseFormat = ResponseFormat.Html; 

      Response.Cache.SetCacheability(HttpCacheability.NoCache); 

      //setup user object 
      this.CurrentUser = WebUser.CurrentUser; 
      ViewData["CurrentUser"] = WebUser.CurrentUser; 
     } 
    } 

    public enum ResponseFormat 
    { 
     Html, 
     Json, 
     Xml 
    } 
} 

我的jquery：

$.ajax({ 
    type: "GET", 
    contentType: "application/json; charset=utf-8", 
    url: "/Vendor/Details/" + newid, 
    data: "{}", 
    dataType: "json", 
    success: function(data) { ShowVendor(data); }, 
    error: function(req, status, err) { ShowError("Sorry, an error occured (Vendor callback failed). Please try agian later."); } 
}); 

Answer 1

它看起来像你想使用的ContentType头，以确定要返回的响应的类型。这不是它的目的。您应该使用Accepts标头，它会告诉服务器您接受哪些内容类型。

Answer 2

“内容类型” 头没有做任何事情，当你的方法是 “GET”。

Answer 3

尝试使用

$.ajax({ 
      type: "GET", 
      contentType: "application/json; charset=utf-8", 
      url: "/Vendor/Details/" + newid, 
      beforeSend: function(xhr) { 
       xhr.setRequestHeader("Content-type", 
        "application/json; charset=utf-8"); 
      }, 
      data: "{}", 
      dataType: "json", 
      success: function(data) { alert(data); }, 
      error: function(req, status, err) { ShowError("Sorry, an error occured (Vendor callback failed). Please try agian later."); } 
     }); 

一拉 - http://encosia.com/2008/06/05/3-mistakes-to-avoid-when-using-jquery-with-aspnet-ajax/