WCF Web API preview 6: No 'MediaTypeFormatter' is available

问题

I'm looking at using HttpClient in WCF Web API Preview 6 to consume a third party service. This third party service accepts and returns XML formatted data. Their HTTP responses have the Content-Type header set to text/plain. It appears that having the response Content-Type set to text/plain is causing problems. I'm making the request to the service as follows:

Task<HttpResponseMessage> result = client.PostAsync(apiEndpoint, new ObjectContent(typeof (LeaveAccrualRequest), request));

Using Fiddler, I can see the request go to the service and an appropriate, expected response come back. However when I try to access the response, I end up with the following InvalidOperationException:

No 'MediaTypeFormatter' is available to read an object of type 'LeaveAccrualResponse' with the media type 'text/plain'.

Is there a way to tell HttpClient that even though the HTTP response says the content type is text/plain, it should handle it as application/xml?

回答1:

You could derive from XmlMediaTypeFormatter and add your "text/plain" header:

public class TextPlainXmlMediaTypeFormatter : XmlMediaTypeFormatter {
    public TextPlainXmlMediaTypeFormatter() {
        SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/plain"));
    }
}

Depending on your requirements it could make sense to remove all other supported media types before adding "text/plain:

SupportedMediaTypes.Clear();

[Update]

Access your requests Content and use the ReadAsAsync<T> method overlaod which accepts an IEnumerable<MediaTypeFormatter>.

来源：https://stackoverflow.com/questions/8367871/wcf-web-api-preview-6-no-mediatypeformatter-is-available