c# - 何时处理 HttpResponseMessage 或 HttpContent

Question

我正在设置一个 API 来与数据库交互，当该 API 收到一个帖子以创建一个已经存在于它的相应表中的条目时，我想返回一个带有解释性消息的代码 209 冲突。所以我尝试了这个:

Controller

public async Task<IHttpActionResult> PostOrganizationAsync(Organization organization)
{
    using (var context = new ContextHandler())
    {
        bool added = await context.AddOrganizationAsync(organization);
        if (added)
        {
            return Ok();
        }
        else
        {
            using (var httpContent = new StringContent("An organization with this Id already exists on the database"))
            {
                return new CustomHttpResponse(HttpStatusCode.Conflict, httpContent);
            }
        }
    }
}

上下文处理器

class ContextHandler : IDisposable
{
    static AuditLogsEntities LogDatabaseContext;

    public ContextHandler()
    {
        LogDatabaseContext = new AuditLogsEntities();
        LogDatabaseContext.Configuration.LazyLoadingEnabled = false;
    }

    public void Dispose()
    {
        LogDatabaseContext.Dispose();
    }

    public async Task<bool> AddOrganizationAsync(Organization organization)
    {
        var findOrg = await LogDatabaseContext.OrganizationSet.FindAsync(organization.Id);
        if (findOrg != null)
        {
            return false;
        }
        else
        {
            LogDatabaseContext.OrganizationSet.Add(organization);
            await LogDatabaseContext.SaveChangesAsync();
            return true;
        }
    }
}

CustomHttpResponse

public class CustomHttpResponse : IHttpActionResult
    {
        public HttpStatusCode StatusCode;
        public HttpContent Content;

        public CustomHttpResponse(HttpStatusCode httpStatusCode, HttpContent httpContent)
        {
            StatusCode = httpStatusCode;
            Content = httpContent;
        }

#pragma warning disable CS1998 // Async method lacks 'await' operators and will run synchronously
        public async Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
#pragma warning restore CS1998 // Async method lacks 'await' operators and will run synchronously
        {
            HttpResponseMessage httpResponse = null;
            using (httpResponse = new HttpResponseMessage(StatusCode))
            {
                httpResponse.Content = Content;
                return httpResponse;
            }         
        }
    }

发布一个新的有效条目工作正常，但尝试发布一个已经存在的条目来测试 209 响应会导致 ObjectDisposedException，我认为这是因为我的一个使用 block ，但问题是我不确定它是哪个 block 以及它为什么会导致错误。

编辑:不知何故，我现在才意识到，根据 StackTrace，当 private HttpRequestMessage _request 属性被设置在 HttpResponseMessage

时会抛出异常

Answer 1

不要使用 using block 。只需将它们存储在一个私有(private)变量中，然后通过 Controller 处理来处理它们。此外，您可以对已完成的任务使用 Task.FromResult。

Controller

private StringContent _httpContent
private CustomHttpResponse _customHttpResponse

public async Task<IHttpActionResult> PostOrganizationAsync(Organization organization)
{
    using (var context = new ContextHandler())
    {
        bool added = await context.AddOrganizationAsync(organization);
        if (added)
        {
            return Ok();
        }
        else
        {
            this._httpContent = new StringContent("An organization with this Id already exists on the database"))
            this._customHttpResponse = new CustomHttpResponse(HttpStatusCode.Conflict, httpContent);
            return this._customHttpResponse;
        }
    }
}

protected override void Dispose(bool disposing)
{
    if (disposing)
    {
        if (this._httpContent != null)
        {
            this._httpContent.Dispose();
        }
        if (this._customHttpResponse != null)
        {
            this._customHttpResponse.Dispose();
        }
    }
}

CustomHttpResponse

public class CustomHttpResponse : IHttpActionResult
{
    public HttpStatusCode StatusCode;
    public HttpContent Content;

    public CustomHttpResponse(HttpStatusCode httpStatusCode, HttpContent httpContent)
    {
        StatusCode = httpStatusCode;
        Content = httpContent;
    }

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        HttpResponseMessage httpResponse = new HttpResponseMessage(StatusCode);
        httpResponse.Content = Content;
        return Task.FromResult(httpResponse);
    }
}