How can i use .net webservice to make login app in android phone app?

i have the Main.xml in layout like this

i have a dologin.java

package ads.login;

import android.app.Activity; import android.os.Bundle; import android.view.View.OnClickListener; import android.view.View; import android.widget.Button; import android.widget.Toast; import android.app.AlertDialog; import android.content.DialogInterface; import android.app.ProgressDialog;

public class DoLogin extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main);

}

}