HttpClient读取ASP.NET Web API错误信息的简单方法

在C#中,用HttpClient调用Web API并且通过Content.ReadAsStringAsync()读取响应内容时,如果出现500错误(InternalServerError),会得到一个包含错误信息的json字符串:

{
    "Message":"An error has occurred.",
    "ExceptionMessage":"",
    "ExceptionType":"",
    "StackTrace":"",
    "InnerException":
    {
        "Message":"",
        "ExceptionMessage":"",
        "ExceptionType":",
        "StackTrace":"",
        "InnerException":
        {
            "Message":"",
            "ExceptionMessage":"",
            "ExceptionType":"",
            "StackTrace":""
        }
    }
}

这样一个复杂的字符串可读性很差,通常只需要部分信息(比如ExceptionMessage)就可以知道错误的情况。

那如何读取所需的部分信息呢?

开始用的是 Microsoft.AspNet.WebApi.Client + dynamic,实现代码如下:

var response = await _httClient.GetAsync(url);
dynamic content = await response.Content.ReadAsAsync<ExpandoObject>();
Console.WriteLine(content.ExceptionMessage);

后来一想,这个json字符串也是某种类型的实例序列化出来的,找到这个类型,然后直接反序列化这个类型的实例,岂不更简单。

找了找,发现原来就是Microsoft.AspNet.WebApi.Core中的HttpError:

namespace System.Web.Http
{
    [XmlRoot("Error")]
    public sealed class HttpError : Dictionary<string, object>, IXmlSerializable
    {
        public HttpError();
        public HttpError(string message);
        public HttpError(ModelStateDictionary modelState, bool includeErrorDetail);
        public HttpError(Exception exception, bool includeErrorDetail);
        public string ExceptionMessage { get; set; }
        public string ExceptionType { get; set; }
        public HttpError InnerException { get; }
        public string Message { get; set; }
        public string MessageDetail { get; set; }
        public HttpError ModelState { get; }
        public string StackTrace { get; set; }
        public TValue GetPropertyValue<TValue>(string key);
    }
}

于是改用下面更简单的实现代码:

var response = await _httClient.GetAsync(url);
Console.WriteLine((await response.Content.ReadAsAsync<HttpError>()).ExceptionMessage);

注:需要nuget安装Microsoft.AspNet.WebApi.Client与Microsoft.AspNet.WebApi.Core

posted @ 2015-08-26 14:56 dudu 阅读(...) 评论(...) 编辑 收藏