从iOS应用程序调用Web服务

我想制作一个简单的iOS应用程序，该应用程序调用Web服务。

我引用了以下链接http://www.codeproject.com/Tips/622376/iOS-Soap-Webservice-Calling-and-Parsing-the-Respon

我试图运行从此链接获得的示例项目。但是我得到的响应像

“ soap：ClientServer无法识别HTTP标头SOAPAction的值：http : //tempuri.org/。”

我无法找出导致此错误的原因。而且我是Web服务的新手。有人可以帮助我解决此错误吗？有人请告诉我，调用Web服务的基本步骤是什么？来自iOS应用程序。调用Web服务是否有Xcode和iOS的特殊版本要求？请帮助我...谢谢您的帮助...

这是我用于发送请求的代码

 NSString *soapMessage = [NSString stringWithFormat:@"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
                             "<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\">\n"
                             "<soap:Body>\n"
                             " <CelsiusToFahrenheit xmlns=\"http://tempuri.org/\">\n"
                             "<Celsius>%@</Celsius>\n"
                             "</CelsiusToFahrenheit>\n"
                             "</soap:Body>\n"
                             "</soap:Envelope>\n" ,textFieldCelcisus.text];


    NSURL *url = [NSURL URLWithString:@"http://w3schools.com/webservices/tempconvert.asmx"];
    NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:url];
    NSString *msgLength = [NSString stringWithFormat:@"%d", [soapMessage length]];

    [theRequest addValue: @"text/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"];
    [theRequest addValue: @"http://tempuri.org/" forHTTPHeaderField:@"SOAPAction"];
    [theRequest addValue: msgLength forHTTPHeaderField:@"Content-Length"];
    [theRequest setHTTPMethod:@"POST"];
    [theRequest setHTTPBody: [soapMessage dataUsingEncoding:NSUTF8StringEncoding]];

    NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

    if( theConnection )
    {
        webData = [NSMutableData data] ;
        NSLog(@"webdata is %@",webData);
        NSLog(@"Problem");
    }
    else
    {
        NSLog(@"theConnection is NULL");
    }