下载Ksoap2.jar,

import  org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.*;
import  org.ksoap2.transport.HttpTransportSE;
import  android.os.Handler;

Handler handler = new Handler() {

    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        Bundle bundle= msg.getData();
        String result=bundle.getString("result");

        Toast.makeText(LoginActivity.this,result,Toast.LENGTH_SHORT).show();
    }
};

new Thread() {
    public void run() {

        String Namespace = "http://tempuri.org/";
        String MethodName = "UserLogin";
        String WEB_SERVICE_URL = "http://192.168.4.2/myWeb/User.asmx";

        SoapObject request = new SoapObject(Namespace, MethodName);
        // 2、设置调用方法的参数值，如果没有参数，可以省略，


        // 3、生成调用Webservice方法的SOAP请求信息。该信息由SoapSerializationEnvelope对象描述
        SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(
                SoapEnvelope.VER12);
        envelope.bodyOut = request;
        // c#写的应用程序必须加上这句
        envelope.dotNet = true;
        HttpTransportSE ht = new HttpTransportSE(WEB_SERVICE_URL);
        // 使用call方法调用WebService方法
        try {

            ht.call(null, envelope);
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            final SoapPrimitive result = (SoapPrimitive) envelope.getResponse();
            if (result != null) {
                Log.d("----收到的回复----", result.toString());


                Message message=new Message();
                Bundle bundle=new Bundle();
                bundle.putString("result",result.toString());
                message.setData(bundle);
                handler.sendMessage(message);


            }


        } catch (Exception e) {
            Log.e("----发生错误---", e.getMessage());
            e.printStackTrace();
        }
    }
}.start();

android 调用.NET WebServices