在Entity Framework支持的Web API 2 POST调用中返回一个对象以及409 Conflict错误？

Question

我有一个C#Entity Framework Web API 2控制器.目前,当通过POST方法尝试创建具有相同文本的主文本字段的对象时,我返回409 Conflict错误作为StatusCode结果,以指示添加被视为重复.

我想做的是返回触发重复错误的服务器端对象.所以我需要一些类似于Ok()方法的东西,但是一个变量返回409 Conflict错误作为HTTP状态代码而不是HTTP OK状态代码.

有这样的事吗？我怎样才能做到这一点？如果我可以完成这项工作,客户端在收到409 Conflict错误后不必对服务器进行后续Get调用以获取现有对象.

这是当前的POST方法:

    public IHttpActionResult PostCanonical(Canonical canonical)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        // Check for duplicate Canonical text for the same app name.
        if (db.IsDuplicateCanonical(canonical.AppName, canonical.Text))
        {
            // It's a duplicate.  Return an HTTP 409 Conflict error to let the client know.
            return StatusCode(HttpStatusCode.Conflict);
        }

        db.CanonicalSentences.Add(canonical);
        db.SaveChanges();

        return CreatedAtRoute("DefaultApi", new { id = canonical.ID }, canonical);
    }

Answer 1

你应该退回内容:

return Content(HttpStatusCode.Conflict, original);

Content是ApiController类的方法,它将创建一个NegotiatedContentResult提供HttpStatusCode和内容.无需像在接受的答案中那样在ApiController类上创建自己的扩展方法.

Answer 2

来到这里寻求 ASP.NET Core HTTP 409 的帮助 - 这是相关的，只是解决同一问题的较新方法。

冲突行动结果

 return Conflict(new { message = $"An existing record with the id '{id}' was already found."});

Answer 3

编辑:此解决方案适用于v5之前的WebApi,如果您使用的是v5或更高版本,请参阅此答案.

您可以返回一个NegotiatedContentResult<T>允许您指定状态代码的对象以及要放入http消息正文的对象.

将您的代码更改为以下内容:

public IHttpActionResult PostCanonical(Canonical canonical)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    // Check for duplicate Canonical text for the same app name.
    if (db.IsDuplicateCanonical(canonical.AppName, canonical.Text))
    {
        // It's a duplicate.  Return an HTTP 409 Conflict error to let the client know.
        var original = db.CanonicalSentences.First(c => c.ID == canonical.ID);
        return new NegotiatedContentResult<T>(HttpStatusCode.Conflict, original, this);
    }

    db.CanonicalSentences.Add(canonical);
    db.SaveChanges();

    return CreatedAtRoute("DefaultApi", new { id = canonical.ID }, canonical);
}

或者可以用这样的扩展方法包装它:

public static class HttpActionResultExtensions {
    public static IHttpActionResult StatusCodeWithContent<T>(this ApiController @this, HttpStatusCode statusCode, T content) {
        return new NegotiatedContentResult<T>(statusCode, content, @this);
    }
}

然后像这样使用扩展名:

public IHttpActionResult PostCanonical(Canonical canonical)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    // Check for duplicate Canonical text for the same app name.
    if (db.IsDuplicateCanonical(canonical.AppName, canonical.Text))
    {
        // It's a duplicate.  Return an HTTP 409 Conflict error to let the client know.
        var original = db.CanonicalSentences.First(c => c.ID == canonical.ID);
        return StatusCodeWithContent(HttpStatusCode.Conflict, original)
    }

    db.CanonicalSentences.Add(canonical);
    db.SaveChanges();

    return CreatedAtRoute("DefaultApi", new { id = canonical.ID }, canonical);
}