如果在.Net Web Api 2中使用OwinContext中间件出现错误请求，如何检索实际错误消息？

Question

当 .Net Web API 返回 Badrequest("this is an example of Badrequest".) 时，我的中间件中的 IOwinContext 对象仅包含 context.Response.StatusCode 400 和 context.Response.ReasonPhrase 作为“错误请求”。我想要实际的错误消息，以便我可以在某处记录它。是否可以在不编写任何自定义类的情况下从IOwinContext 获取实际错误消息？

编辑： Startup.cs

public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            ICoreLogger dv_logger = new CoreLogger();
            app.Use<InvalidAuthenticationMiddleware>(dv_logger);
            ConfigureOAuth(app);
            //register log4net
            XmlConfigurator.Configure();
            // configure log4net variables
            GlobalContext.Properties["processId"] = "dv_logger";
            System.Web.Http.GlobalConfiguration.Configure(WebApiConfig.Register);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            //entity framework
            DbContext.Intialize();
            AuthContext.Intialize();
            .....
   }

中间件

 public class InvalidAuthenticationMiddleware : OwinMiddleware
{
        public override async Task Invoke(IOwinContext context)
        {
            var stream = context.Response.Body;
            using (var buffer = new MemoryStream())
            {
                context.Response.Body = buffer;
                await Next.Invoke(context);

                buffer.Seek(0, SeekOrigin.Begin);
                using (var reader = new StreamReader(buffer))
                {
                    string responseBody = await reader.ReadToEndAsync();

                    if (context.Response.StatusCode == (int)HttpStatusCode.BadRequest)
                    {
                        var definition = new { Message = "" };
                        var error = JsonConvert.DeserializeAnonymousType(responseBody, definition);

                        Debug.WriteLine(error.Message);
                    }

                    buffer.Seek(0, SeekOrigin.Begin);
                    await buffer.CopyToAsync(stream);
                }
            }
        }

}

控制器

public class LoginController : BaseController
{
        [Route("")]
        public IHttpActionResult Get(string email)
        {
           return BadRequest("this is an example of bad request!");
        }
}

Answer 1

您必须阅读响应的正文。 BadRequest("this is an example of BadRequest") 在响应正文中设置一个对象，其属性Message 包含该消息。我假设您使用 JSON 作为序列化格式：

{
    "Message": "this is an example of BadRequest"
}

这是在响应为BadRequest 时记录错误消息的中间件代码：

public override async Task Invoke(IOwinContext context)
{
    var stream = context.Response.Body;
    using (var buffer = new MemoryStream())
    {
        context.Response.Body = buffer;

        await next.Invoke();

        buffer.Seek(0, SeekOrigin.Begin);
        using (var reader = new StreamReader(buffer))
        {
            string responseBody = await reader.ReadToEndAsync();

            if (context.Response.StatusCode == (int)HttpStatusCode.BadRequest)
            {
                var definition = new { Message = "" };
                var error = JsonConvert.DeserializeAnonymousType(responseBody, definition);

                Console.WriteLine(error.Message);
            }

            buffer.Seek(0, SeekOrigin.Begin);
            await buffer.CopyToAsync(stream);
        }
    }
}

请注意，我使用匿名类型以避免必须为错误消息对象声明一个类。