WCF Rest服务错误处理和WebChannelFactory

Question

根据我的理解，以下代码应该正确地抛出来自WCF Rest服务的自定义错误：

[DataContract(Namespace = "")]
public class ErrorHandler
{
    [DataMember]
    public int errorCode { get; set; }

    [DataMember]
    public string errorMessage { get; set; }
} // End of ErrorHandler

public class Implementation : ISomeInterface
{
    public string SomeMethod()
    {
        throw new WebFaultException<ErrorHandler>(new ErrorHandler()
        {
            errorCode = 5,
            errorMessage = "Something failed"
        }, System.Net.HttpStatusCode.BadRequest);
    }
}

在Fiddler中，这似乎是可行的，我得到了以下原始数据：

HTTP/1.1 400 Bad Request
Cache-Control: private
Content-Length: 145
Content-Type: application/xml; charset=utf-8
Server: Microsoft-IIS/7.5
X-AspNet-Version: 4.0.30319
Set-Cookie: ASP.NET_SessionId=gwsy212sbjfxdfzslgyrmli1; path=/; HttpOnly
X-Powered-By: ASP.NET
Date: Thu, 03 May 2012 17:49:14 GMT

<ErrorHandler xmlns:i="http://www.w3.org/2001/XMLSchema-instance"><errorCode>5</errorCode><errorMessage>Something failed</errorMessage></ErrorHandler>

但现在在我的客户端，我有以下代码：

WebChannelFactory<ISomeInterface> client = new WebChannelFactory<ISomeInterface>(new Uri(targetHost));

ISomeInterface someInterface = client.CreateChannel();
try
{
  var result = someInterface.SomeMethod();
}
catch(Exception ex)
{
   // Try to examine the ErrorHandler to get additional details.
}

现在，当代码运行时，它命中了catch，它是一个System.ServiceModel.ProtocolException，并显示消息“the remote server returned an unexpected response：(400) Bad Request.”。在这一点上，我似乎没有办法查看ErrorHandler的详细信息。有没有人碰到过这个？有没有办法在这一点上获得ErrorHander的详细信息？

Answer 1

WebChannelFactory或ChannelFactory只会向您透露通用CommunicationException。您将需要使用IClientMessageInspector行为或依靠WebRequest来返回实际的错误。

有关IClientMessageInspector方法-请参阅this blog entry中的注释。

对于WebRequest方法，您可以执行以下操作来捕获WebException。

try { }
catch (Exception ex)
{
    if (ex.GetType().IsAssignableFrom(typeof(WebException)))
    {
        WebException webEx = ex as WebException;
        if (webEx.Status == WebExceptionStatus.ProtocolError)
        {
            using (StreamReader exResponseReader = new StreamReader(webEx.Response.GetResponseStream()))
            {
                string exceptionMessage = exResponseReader.ReadToEnd();
                Trace.TraceInformation("Internal Error: {0}", exceptionMessage);
            }
        }
    }
}