Sometimes, Hello world does not work;)

I add a web method to existing web service, which return array of arraylist as the result.

then everything workes worse, the client can not invoke either of the web method

here is a simple code

public service1: WebService
{
 
public service1()
{
}
        [WebMethod]
        public string HelloWorld()
        {
            return "Hello World, I am running in montaque notebook .NET";
        }
 
        [WebMethod]
        public ArrayList [] TestArrayList()
        {
            ArrayList [] ar=new ArrayList[1];
            ar[0].Add(1);
            ar[0].Add(2);
            return ar;
        }
 
 
}

when I test the code in the .net latest build ,40903, get the same result