WCF will not return an int

Question

I am building a WCF in C#, and a client to consume it at the same time. For some reason I am having trouble getting a method to return an int. Here is my contract:

Answer 1

You import it as a Service Reference (with name space MData) instead Web Reference.

And use the below code,

MDataClient m = new MDataClient(); 
String helloWorld = m.HelloWorld(); 
int result = m.ReturnAnInt();

There is nothing wrong in your code. It should works fine if you add Service Reference and use the above snippet.

Answer 2

Can you import it as a Service Reference (newer tech) instead of a Web Reference (older tech)? I work with WCF services through service references and haven't seen such an issue - I've only seen a Specified property (and that as a property alongside the int, not as two out params) when the service definition allows no int to be specified (WCF-generated service definitions have, in my experience, worked as expected).

If you can't find a better solution, here's a workaround using partial classes: (this would have to be done any time you return a struct, not just ints)

public partial class MData
{
    public int ReturnAnInt()
    {
        int result;
        bool specified;
        this.ReturnAnInt(out result, out specified);
        if (!specified) throw new InvalidOperationException();
        return result;
    }
}

Update http://www.codeproject.com/Articles/323097/WCF-ASMX-Interoperability-Removing-the-Annoying-xx has a (somewhat klunky) solution, and informs us that the root cause is that WCF generates poor (arguably inaccurate) WSDLs - they have a minOccurs="0" on elements that really don't need it. Web References reads this as-is, and generates klunky code to deal with it, which is what you're trying to deal with. Based on his article, you can return this type instead of an int:

[MessageContract(IsWrapped = false)]
public class MyInt
{
    [MessageBodyMember]
    public int Result { get; set; }

    public static implicit operator MyInt(int i)
    {
        return new MyInt { Result = i };
    }

    public static implicit operator int(MyInt m)
    {
        return m.Result;
    }
}

Along with modifying the return type of the method:

[ServiceContract]
public interface IMData
{
    [OperationContract]
    MyInt ReturnAnInt();

    [OperationContract]
    String HelloWorld();
}
public class Service1 : IMData
{
    public MyInt ReturnAnInt()
    {
        return 4;
    }

    public string HelloWorld()
    {
        return "Hello World";
    }
}

Answer 3

I had a similar issue, I could not get an out int parameter of my web service to work. I am still not sure due to what this was exactly, but I had it working using a string as out parameter.

[OperationContract]
LoginStatus GetLogin(string username, string password, out string s_uId);

on the web service side:

s_uId = uId.ToString();

on the client side:

int uId;
string s_uId;
result = client.GetLogin(username, password, out s_uId);
Int32.TryParse(s_uId, out uId);