首先添加WebService服务端方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;

namespace WebApplication2
{
    /// <summary>
    /// WebService1 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 WebService1 : System.Web.Services.WebService
    {

        [WebMethod]
        public string HelloWorld()
        {
            return "Hello World";
        }
        [WebMethod (EnableSession = true)]//标记为服务方法
        public string CountSum(string param1, string param2)
        {

            decimal num1 = Convert.ToInt32(param1);
            decimal num2 = Convert.ToInt32(param2);

            decimal sum = num1 + num2;

            return sum.ToString();



        }

    }
}

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Collections;
using System.Web;
using System.Net;
using System.Reflection;
using System.CodeDom;
using System.CodeDom.Compiler;
using System.Text;
using System.Web.Services.Description;
using System.Xml.Serialization;
using System.Windows.Forms;
using System.Xml;

namespace WebServiceForm
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {

            //cn.com.webxml.www.WeatherWebService weatherWebService = new cn.com.webxml.www.WeatherWebService();
            //string[] vsArr = weatherWebService.getWeatherbyCityName(this.textBox1.Text);
            //localhost.WebService1 webService1 = new localhost.WebService1();
            //this.textBox2.Text = webService1.HelloWorld();

            //this.textBox1.Text = Convert.ToString(webService1.HelloWorld());

            //ServiceReference1.CalculateServiceClient calculateServiceClient = new ServiceReference1.CalculateServiceClient();

            //this.textBox2.Text = Convert.ToString(calculateServiceClient.AddSum(10, 10));
            //localhost2.CalculateService calculateService = new localhost2.CalculateService();
            //this.textBox2.Text = Convert.ToString(calculateService.AddSum(1,1));

            //var client = new HttpClient();
            //client.BaseAddress = new Uri("http://localhost:22650/");

            //var str =await client.GetStringAsync("WebApplication4/News/GetAllNews");


            //第一种采用动态代理

            //反射、CodeDom
            WebClient webClient = new WebClient();
            string url = "http://localhost:10925/WebService1.asmx?WSDL";//可以取。我记得k3cloud有专门设置地址的单据，对接其他系统的
            //http://localhost:10925/

            Stream stream = webClient.OpenRead(url);

            ServiceDescription serviceDescription = ServiceDescription.Read(stream);

            ServiceDescriptionImporter importer = new ServiceDescriptionImporter();//创建客户端代理类
            importer.ProtocolName = "Soap";
            importer.Style = ServiceDescriptionImportStyle.Client;//生成客户端代理

            importer.CodeGenerationOptions = CodeGenerationOptions.GenerateProperties | CodeGenerationOptions.GenerateNewAsync;
            importer.AddServiceDescription(serviceDescription, "", "");

            CodeNamespace codeNamespace = new CodeNamespace();//命名空间 

            codeNamespace.Name = "TestWebservice";
            CodeCompileUnit codeCompileUnit = new CodeCompileUnit();
            codeCompileUnit.Namespaces.Add(codeNamespace);
            ServiceDescriptionImportWarnings warnings = importer.Import(codeNamespace, codeCompileUnit);

            CodeDomProvider provider = CodeDomProvider.CreateProvider("CSharp");

            CompilerParameters parameters = new CompilerParameters();

            parameters.GenerateExecutable = false;
            parameters.OutputAssembly = "MyTest.dll";
            parameters.ReferencedAssemblies.Add("System.dll");
            parameters.ReferencedAssemblies.Add("System.XML.dll");
            parameters.ReferencedAssemblies.Add("System.Web.Services.dll");
            parameters.ReferencedAssemblies.Add("System.Data.dll");

            CompilerResults results = provider.CompileAssemblyFromDom(parameters, codeCompileUnit);

            if (results.Errors.HasErrors)
            {
            }

            Assembly assembly = Assembly.LoadFrom("MyTest.dll");
            Type t = assembly.GetType("TestWebservice.WebService1");
            object o = Activator.CreateInstance(t);
            MethodInfo methodInfo = t.GetMethod("HelloWorld");
            string str = Convert.ToString(methodInfo.Invoke(o, null));
            this.textBox2.Text = str;

            //第二种利用http 协议的get  和post，HttpWebRequest，HttpWebResponse,Stream
            string url2 = "http://localhost:10925/WebService1.asmx";
            string result = "";
            string param = "";
            byte[] bytes= null;
            Stream requeststream = null;
            HttpWebRequest httpWebRequest = null;
            HttpWebResponse httpWebResponse = null;
            decimal num1 = 1, num2 = 4;
            param  = HttpUtility.UrlEncode("param1") + "=" +
                HttpUtility.UrlEncode(Convert.ToString(num1)) + "&" +
                HttpUtility.UrlEncode("param2") + "=" + 
                HttpUtility.UrlEncode(Convert.ToString(num2));
            bytes = Encoding.UTF8.GetBytes(param);
            httpWebRequest =(HttpWebRequest)WebRequest.Create(url2 + "/"+ "CountSum");

            httpWebRequest.Method = "POST";

            httpWebRequest.ContentType= "application/x-www-form-urlencoded";

            httpWebRequest.ContentLength = bytes.Length;

            requeststream = httpWebRequest.GetRequestStream();
            requeststream.Write(bytes,0, bytes.Length);
            requeststream.Close();
            try
            {
                httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

            Stream ResponseStream = httpWebResponse.GetResponseStream();

            XmlTextReader xmlTextReader = new XmlTextReader(ResponseStream);
            xmlTextReader.MoveToContent();
            result = xmlTextReader.ReadInnerXml();

            //StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream(),Encoding.UTF8);

            //result = streamReader.ReadToEnd();


            this.textBox1.Text = result;
            requeststream.Dispose();
            requeststream.Close();
            ResponseStream.Dispose();

            ResponseStream.Close();


            httpWebResponse.Dispose();
            httpWebResponse.Close();

            xmlTextReader.Dispose();
            xmlTextReader.Close();




        }
    }
}

最后结果

 与添加Web引用对比

    通常我们在程序中需要调用WebService时，都是通过“添加Web引用”，让VS.NET环境来为我们生成服务代理，然后调用对应的Web服务。这样是使工作简单了，但是却和提供Web服务的URL、方法名、参数绑定在一起了，这是VS.NET自动为我们生成Web服务代理的限制。如果哪一天发布Web服务的URL改变了，则我们需要重新让VS.NET生成代理，并重新编译。在某些情况下，这可能是不能忍受的，我们需要动态调用WebService的能力。比如我们可以把Web服务的URL保存在配置文件中，这样，当服务URL改变时，只需要修改配置文件就可以了