Invoking Web Method Using iOS

问题

I am trying to invoke a web method "Greet" which takes multiple arguments as shown below:

 [WebMethod]
        public string Greet(string deviceToken,string userName)
        {
           // do something

            return "Hello World";
        }

And here is my iOS code to invoke the service. When I invoke I always get "Internal Error 500".

-(IBAction)submitButtonClicked:(id)sender
{
    // call the web service 
    //21212d6fefebde4d317cab41afff65631b5a4d47e5d85da305ec610b4013e616;

    NSURL *url = [NSURL URLWithString:@"http://www.azamsharp.com/NotificationService.asmx?op=Greet"];
    ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url]; 
    [request setRequestMethod:@"POST"];
    [request addRequestHeader:@"Content-Type" value:@"text/xml; charset=utf-8"];



    [request setPostValue:@"2122132d6fefe243bde4d234317cab41a234f234ff65631b5a4d47e5d85da305ec610b4013e616" forKey:@"deviceToken"]; 
    [request setPostValue:@"azamsharp" forKey:@"userName"]; 

    [request setDelegate:self]; 
    [request startAsynchronous]; 


}

来源：https://stackoverflow.com/questions/7084996/invoking-web-method-using-ios