从 Web Api 控制器返回 http 状态码

我不知道答案，所以问 ASP.NET 团队 here。

所以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);
}

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如果要将操作签名保留为返回用户，还可以执行以下操作：

public User GetUser(int userId, DateTime lastModifiedAtClient) 

如果您想返回 200 以外的内容，则在您的操作中抛出一个 HttpResponseException 并传入您要发送给客户端的 HttpResponseMessage。

---

更改 GetXxx API 方法以返回 HttpResponseMessage，然后返回完整响应的类型化版本和 NotModified 响应的非类型化版本。

    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。

笔记

我认为通用版本将在 Web API 的某些未来版本中被删除。

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在 MVC 5 中，事情变得更容易了：

return new StatusCodeResult(HttpStatusCode.NotModified, this);

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对于 ASP.NET Web Api 2，this post from MS 建议将方法的返回类型更改为 IHttpActionResult。然后，您可以返回内置的 IHttpActionResult 实现，如 Ok、BadRequest 等 (see here) 或返回您自己的实现。

对于您的代码，可以这样做：

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);
}

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我讨厌撞旧文章，但这是谷歌搜索中的第一个结果，我有一段时间解决这个问题（即使在你们的支持下）。所以这里什么都没有...

希望我的解决方案能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 状态码。这是使用 ApiController。

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

您可以选择返回一个带有响应的对象

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

---

我不喜欢更改我的签名来使用 HttpCreateResponse 类型，所以我想出了一些扩展的解决方案来隐藏它。

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，您可以向您的 ApiController（或更好的基本控制器）添加一个方法，如下所示：

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

然后你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." 
                });
}

---

尝试这个 ：

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

---

如果您需要返回 IHttpActionResult 并希望返回错误代码和消息，请使用：

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

---

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;
}

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使用 Web API 2 中引入的更现代的 IHttpActionResult 更新 @Aliostads 答案。

https://docs.microsoft.com/en-us/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);
    }
}

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我知道这里有几个很好的答案，但这是我需要的，所以我想我会添加此代码，以防其他人需要使用 webAPI 在 4.7.x 中返回他们想要的任何状态代码和响应正文。

public class DuplicateResponseResult<TResponse> : IHttpActionResult
{
    private TResponse _response;
    private HttpStatusCode _statusCode;
    private HttpRequestMessage _httpRequestMessage;
    public DuplicateResponseResult(HttpRequestMessage httpRequestMessage, TResponse response, HttpStatusCode statusCode)
    {
        _httpRequestMessage = httpRequestMessage;
        _response = response;
        _statusCode = statusCode;
    }

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        var response = new HttpResponseMessage(_statusCode);
        return Task.FromResult(_httpRequestMessage.CreateResponse(_statusCode, _response));
    }
}

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