How to pass value from web service to Asyn method.?

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web

I have webservice and windows phone app. I need to pass an variable from web service to windows phone app
Web service:

public String ValidateQuery(string name, string password)
      {
          string s="";
          OleDbConnection con2 = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Amma\Documents\UserData.accdb");
          OleDbCommand cmd = new OleDbCommand("SELECT count(*) from login WHERE name='" + name + "' and pwd='" + password + "'", con2);
          con2.Open();
          OleDbDataReader da = cmd.ExecuteReader();
          while (da.Read())
          {
              if (da.HasRows == true)
              {
                  s = "OK";
                  break;
              }
              else
              {
                  s = "Not Ok"; // I need to pass this variable.
                  break;
              }
          }

My WP7 mehtod:
Test.xaml.cs

private void btnLogin_Click(object sender, RoutedEventArgs e)
{
    string uname=textBoxName.Text;
    string pwd=textBoxPwd.Text;
    myService.Service1SoapClient client = new Service1SoapClient();
   client.ValidateCompleted += new EventHandler<ValidateCompletedEventArgs>(client_ValidateCompleted);
    client.UpdateQueryAsync(uname, pwd);
    string result= // here i need get that string here.

}

If ther any other to achieve this action pls help me.