从Web Api控制器返回http状态代码

我试图返回状态304，但未在网络api控制器中为GET方法修改。

我成功的唯一方法是这样的：

public class TryController : ApiController
{
    public User GetUser(int userId, DateTime lastModifiedAtClient)
    {
        var user = new DataEntities().Users.First(p => p.Id == userId);
        if (user.LastModified <= lastModifiedAtClient)
        {
             throw new HttpResponseException(HttpStatusCode.NotModified);
        }
        return user;
    }
}

这里的问题是，这不是一个例外，它没有被修改，因此客户端缓存正常。我还希望返回类型为User（如所有Web API示例使用GET所示）不返回HttpResponseMessage或类似的内容。

我不知道答案，所以在这里问ASP.NET团队。

因此，诀窍是将签名更改为HttpResponseMessage并使用Request.CreateResponse。

[ResponseType(typeof(User))]
public HttpResponseMessage GetUser(HttpRequestMessage request, int userId, DateTime lastModifiedAtClient)
{
    var user = new DataEntities().Users.First(p => p.Id == userId);
    if (user.LastModified <= lastModifiedAtClient)
    {
         return new HttpResponseMessage(HttpStatusCode.NotModified);
    }
    return request.CreateResponse(HttpStatusCode.OK, user);
}

如果要将动作签名保留为返回用户，也可以执行以下操作：

public User GetUser(int userId, DateTime lastModifiedAtClient) 

如果您想返回其他内容，200则可以执行一个HttpResponseException操作，然后将HttpResponseMessage您要发送的内容传递给客户端。

在MVC 5中，事情变得更容易了：

return new StatusCodeResult(HttpStatusCode.NotModified, this);

更改GetXxx API方法以返回HttpResponseMessage，然后为完整响应返回带类型的版本，为NotModified响应返回带类型的版本。

    public HttpResponseMessage GetComputingDevice(string id)
    {
        ComputingDevice computingDevice =
            _db.Devices.OfType<ComputingDevice>()
                .SingleOrDefault(c => c.AssetId == id);

        if (computingDevice == null)
        {
            return this.Request.CreateResponse(HttpStatusCode.NotFound);
        }

        if (this.Request.ClientHasStaleData(computingDevice.ModifiedDate))
        {
            return this.Request.CreateResponse<ComputingDevice>(
                HttpStatusCode.OK, computingDevice);
        }
        else
        {
            return this.Request.CreateResponse(HttpStatusCode.NotModified);
        }
    }

* ClientHasStale数据是我用于检查ETag和IfModifiedSince标头的扩展。

MVC框架仍应序列化并返回您的对象。

注意

我认为通用版本会在将来的Web API版本中删除。

我讨厌碰碰旧文章，但这是google搜索的第一个结果，而且我在这个问题上花了很长时间（即使在你们的支持下）。所以这里什么都没有...

希望我的解决方案可以帮助那些也感到困惑的人。

namespace MyApplication.WebAPI.Controllers
{
    public class BaseController : ApiController
    {
        public T SendResponse<T>(T response, HttpStatusCode statusCode = HttpStatusCode.OK)
        {
            if (statusCode != HttpStatusCode.OK)
            {
                // leave it up to microsoft to make this way more complicated than it needs to be
                // seriously i used to be able to just set the status and leave it at that but nooo... now 
                // i need to throw an exception 
                var badResponse =
                    new HttpResponseMessage(statusCode)
                    {
                        Content =  new StringContent(JsonConvert.SerializeObject(response), Encoding.UTF8, "application/json")
                    };

                throw new HttpResponseException(badResponse);
            }
            return response;
        }
    }
}

然后从BaseController继承

[RoutePrefix("api/devicemanagement")]
public class DeviceManagementController : BaseController
{...

然后使用它

[HttpGet]
[Route("device/search/{property}/{value}")]
public SearchForDeviceResponse SearchForDevice(string property, string value)
{
    //todo: limit search property here?
    var response = new SearchForDeviceResponse();

    var results = _deviceManagementBusiness.SearchForDevices(property, value);

    response.Success = true;
    response.Data = results;

    var statusCode = results == null || !results.Any() ? HttpStatusCode.NoContent : HttpStatusCode.OK;

    return SendResponse(response, statusCode);
}

.net core 2.2返回304状态代码。这是使用ApiController。

    [HttpGet]
    public ActionResult<YOUROBJECT> Get()
    {
        return StatusCode(304);
    }

（可选）您可以返回带有响应的对象

    [HttpGet]
    public ActionResult<YOUROBJECT> Get()
    {
        return StatusCode(304, YOUROBJECT); 
    }

对于ASP.NET Web Api 2，MS的这篇文章建议将方法的返回类型更改为IHttpActionResult。然后，您可以返回一个内置的IHttpActionResult实现一样Ok，BadRequest等（见这里），还是返回自己的实现。

对于您的代码，可以这样完成：

public IHttpActionResult GetUser(int userId, DateTime lastModifiedAtClient)
{
    var user = new DataEntities().Users.First(p => p.Id == userId);
    if (user.LastModified <= lastModifiedAtClient)
    {
        return StatusCode(HttpStatusCode.NotModified);
    }
    return Ok(user);
}

另外的选择：

return new NotModified();

public class NotModified : IHttpActionResult
{
    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        var response = new HttpResponseMessage(HttpStatusCode.NotModified);
        return Task.FromResult(response);
    }
}

public HttpResponseMessage Post(Article article)
{
    HttpResponseMessage response = Request.CreateResponse<Article>(HttpStatusCode.Created, article);

    string uriToTheCreatedItem = Url.Route(null, new { id = article.Id });
    response.Headers.Location = new Uri(Request.RequestUri, uriToTheCreatedItem);

    return response;
}

如果您需要返回一个IHttpActionResult并想返回错误代码和一条消息，请使用：

return ResponseMessage(Request.CreateErrorResponse(HttpStatusCode.NotModified, "Error message here"));

我不想更改自己的签名以使用HttpCreateResponse类型，因此我想出了一些扩展解决方案来隐藏它。

public class HttpActionResult : IHttpActionResult
{
    public HttpActionResult(HttpRequestMessage request) : this(request, HttpStatusCode.OK)
    {
    }

    public HttpActionResult(HttpRequestMessage request, HttpStatusCode code) : this(request, code, null)
    {
    }

    public HttpActionResult(HttpRequestMessage request, HttpStatusCode code, object result)
    {
        Request = request;
        Code = code;
        Result = result;
    }

    public HttpRequestMessage Request { get; }
    public HttpStatusCode Code { get; }
    public object Result { get; }

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        return Task.FromResult(Request.CreateResponse(Code, Result));
    }
}

然后，您可以像下面这样向ApiController（或更好的基本控制器）添加一个方法：

protected IHttpActionResult CustomResult(HttpStatusCode code, object data) 
{
    // Request here is the property on the controller.
    return new HttpActionResult(Request, code, data);
}

然后，您可以像任何内置方法一样返回它：

[HttpPost]
public IHttpActionResult Post(Model model)
{
    return model.Id == 1 ?
                Ok() :
                CustomResult(HttpStatusCode.NotAcceptable, new { 
                    data = model, 
                    error = "The ID needs to be 1." 
                });
}

@Aliostads的更新使用IHttpActionResultWeb API 2中引入的更现代的方式回答。

https://docs.microsoft.com/zh-cn/aspnet/web-api/overview/getting-started-with-aspnet-web-api/action-results#ihttpactionresult

public class TryController : ApiController
{
    public IHttpActionResult GetUser(int userId, DateTime lastModifiedAtClient)
    {
        var user = new DataEntities().Users.First(p => p.Id == userId);
        if (user.LastModified <= lastModifiedAtClient)
        {
            return StatusCode(HttpStatusCode.NotModified);
            // If you would like to return a Http Status code with any object instead:
            // return Content(HttpStatusCode.InternalServerError, "My Message");
        }
        return Ok(user);
    }
}

试试这个 ：

return new ContentResult() { 
    StatusCode = 404, 
    Content = "Not found" 
};