菜鸟请教高手个问题！！紧急！sliverligt 获取webservice返回值问题

Question

silverlight页面的代码  

private void enter_Click(object sender, RoutedEventArgs e)
  {
  Service1SoapClient client = new Service1SoapClient();
  string name = this.Name.Text;
  string pwd = this.Pwd.Password;
  int i=client.select_adminAsync(name,pwd);

  }

webservice页面的代码


 [WebMethod]
  public int select_admin(string name,string pwd)
  {
  string sql = "select * from admin where Name='" + name + "'and Password='" + pwd + "'";
  DataSet ds = DbHelpSQL.ExecuteGetData(sql);
  if (ds.Tables[0].Rows.Count > 0)
  {
  return 1;
  }
  else
  {
  return 0;
  }

为什么调用方法的时候会说无法将void隐士转换为int 我方法的返回值明明是int 该怎么样才可以调用或者获取返回值