ASP.NET

private const string ProductionUrl  = "http://server1/folder1/MyService/MyService1.asmx";
private const string DevelopmentUrl = "http://server2/folder1/MyService/MyService1.asmx";
private const string LocalHostUrl   = "http://localhost:55179/MyService1.asmx";

switch (Application.Current.Host.Source.Host.ToLower())
{
    case "server1" : CurrentUrl = ProductionUrl;  break;
    case "server2" : CurrentUrl = DevelopmentUrl; break;
    default        : CurrentUrl = LocalHostUrl;   break;
}

// for testing
CurrentUrl = DevelopmentUrl;

service = new ProjNamespace.Service1Reference.Service1SoapClient("Service1Soap", CurrentUrl);
service.GetServiceVersionCompleted += new EventHandler<ProjNamespace.Service1Reference.GetServiceVersionCompletedEventArgs>
                                      (service_GetServiceVersionCompleted);
service.GetServiceVersionAsync();