安卓代码：

import android.os.Handler;
import android.os.Message;


import org.ksoap2.SoapEnvelope;
import org.ksoap2.SoapFault;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;

public class WebServiceUtils {
    public interface CallBack {
        void result(String result);
    }
    //参数说明，serviceUrl是.net的webservice地址，一般取得是http://IP地址：端口号/XXX.asmx
    // methodName 是WebService上的接口名
   // okparams 是 传递的参数以String的形式传递，传递Json可以先转为字符串，服务端再解析出来
   //CallBack回调，获取返回的值
    public static void getResult(final String serviceUrl,final String methodName,final String okparams, final CallBack callBack) {
        // 用于子线程与主线程通信的Handler
        final Handler mHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                // 将返回值回调到callBack的参数中
                callBack.result((String) msg.obj);
            }
        };
        new Thread(new Runnable() {
            @Override
            public void run() {

                try{
                    //.net上的命名空间+webwervice上的方法名
                    String soapAction = "http://tempuri.org/" + methodName;
                   //参数，命名空间，方法名
                    SoapObject request = new SoapObject("http://tempuri.org/", methodName);
                    //传递的参数，注意key要与.net方法的参数名一致
                    request.addProperty("okparams",okparams );
                    SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
                    envelope.bodyOut = request;
                    HttpTransportSE ht = new HttpTransportSE(serviceUrl);
                    ht.call(soapAction, envelope);
                    Object object;
                    if (envelope.getResponse() != null){
                        object  =   (Object)envelope.getResponse();
                        //   SoapObject soapObject = (SoapObject) envelope.getResponse();
                        // 将结果利用Handler发送到主线程
                        mHandler.sendMessage(mHandler.obtainMessage(1, object.toString()));

                    }
                    if (envelope.bodyIn instanceof SoapFault) {
                        SoapFault error = (SoapFault) envelope.bodyIn;
                        // 将异常的消息利用Handler发送到主线程
                        mHandler.sendMessage(mHandler.obtainMessage(0, error.toString()));
                    } 

                }catch (Exception ex)
                {
                    mHandler.sendMessage(mHandler.obtainMessage(-1, ex.getMessage()));
                }

            }
        }).start();
    }
}



//使用实例

WebServiceUtils.getResult(serviceUrl, methodName, 传递的参数, new WebServiceUtils.CallBack() {
    @Override
    public void result(String result) {
        //返回值
        String res = result;
      
    }
});


//.Net部分代码

/// <summary>
/// test 的摘要说明
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
// 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消注释以下行。
// [System.Web.Script.Services.ScriptService]
public class test : System.Web.Services.WebService
{

     [WebMethod]

    public string HelloWorld(string okparams)
   {

        return "Hello World";
  }

  

 

}