What if you encounter a problem when consume your WCF service ? How to Diagnostic it ?

The Answer is the Log Tracing the WCF .

My service is:

[OperationContract(Name="Add")]
[WebInvoke(UriTemplate = "test/", Method = "POST",
          ResponseFormat=WebMessageFormat.Json,
          RequestFormat=WebMessageFormat.Json )]
public int Add(Number n1)
{
    res = Convert.ToInt32(n1.Number1) + Convert.ToInt32(n1.Number2);
    return res;
}

　　

Data are..

[Serializable]
    public class Number
    {
        public int Number1 { get; set; }
        public int Number2 { get; set; }
    }

　　

When I call from fiddler its return ‘HTTP/1.1 400 Bad Request’

My fiddler request header is:

User-Agent: Fiddler
Host: localhost:4217
Content-Type: application/json; charset=utf-8

And request body is:

{"Number1":"7","Number2":"7"}

And response header is:

HTTP/1.1 400 Bad Request
Server: ASP.NET Development Server/10.0.0.0
Date: Sun, 14 Aug 2011 18:10:21 GMT
X-AspNet-Version: 4.0.30319
Content-Length: 5450
Cache-Control: private
Content-Type: text/html
Connection: Close

The way you'll find out the issue with your code is to enable tracing on the server, and it will have an exception explaining the problem. I wrote a simple test with your code, and it had a similar error (400), and the traces had the following error:

The data contract type 'WcfForums.StackOverflow_7058942+Number' cannot be
deserialized because the required data members '<Number1>k__BackingField,
<Number2>k__BackingField' were not found.

See Also

http://msdn.microsoft.com/en-us/library/ms733025.aspx