动态调用WebService时如何保持Session

我按照网上介绍的方法进行WebService的动态调用，然而如果WebService方法中包含有操作Session的动作，则前后动作之间无法保持Session。一直困惑与此，不止如何解决，望各位老师给予指点。

如下是动态调用WebService的方法：
    public object InvokeWebservice(string url,string @namespace,string classname,string methodname,object[] args)
    {
        try
        {
            System.Net.WebClient wc = new System.Net.WebClient();

            System.IO.Stream stream = wc.OpenRead(url + "?WSDL");

            System.Web.Services.Description.ServiceDescription sd
                = System.Web.Services.Description.ServiceDescription.Read(stream);

            System.Web.Services.Description.ServiceDescriptionImporter sdi
                = new System.Web.Services.Description.ServiceDescriptionImporter();

            sdi.AddServiceDescription(sd,"","");

            System.CodeDom.CodeNamespace cn = new System.CodeDom.CodeNamespace(@namespace);
            System.CodeDom.CodeCompileUnit ccu = new System.CodeDom.CodeCompileUnit();

            ccu.Namespaces.Add(cn);
            sdi.Import(cn,ccu);

            Microsoft.CSharp.CSharpCodeProvider csc = new Microsoft.CSharp.CSharpCodeProvider();
            System.CodeDom.Compiler.ICodeCompiler icc = csc.CreateCompiler();

            System.CodeDom.Compiler.CompilerParameters cplist
                = new System.CodeDom.Compiler.CompilerParameters();

            cplist.GenerateExecutable = false;
            cplist.GenerateInMemory = true;

            cplist.ReferencedAssemblies.Add("System.dll");
            cplist.ReferencedAssemblies.Add("System.XML.dll");
            cplist.ReferencedAssemblies.Add("System.Web.Services.dll");
            cplist.ReferencedAssemblies.Add("System.Data.dll");

            System.CodeDom.Compiler.CompilerResults cr = icc.CompileAssemblyFromDom(cplist,ccu);
            if (true == cr.Errors.HasErrors)
            {
                System.Text.StringBuilder sb = new System.Text.StringBuilder();
                foreach (System.CodeDom.Compiler.CompilerError ce in cr.Errors)
                {
                    sb.Append(ce.ToString());
                    sb.Append(System.Environment.NewLine);
                }

                throw new Exception(sb.ToString());
            }

            System.Reflection.Assembly assembly = cr.CompiledAssembly;
            Type t = assembly.GetType(@namespace + "." + classname,true,true);
            object obj = Activator.CreateInstance(t);
            System.Reflection.MethodInfo mi = t.GetMethod(methodname);
            return mi.Invoke(obj,args);
        }

        catch (Exception ex)
        {
            throw ex;
        }
    }



如下是WebService中的两个方法：
    [WebMethod(EnableSession=true)]
    public bool Authenticate(string uid,string pwd)
    {
        if (uid == pwd)
        {
            Session["authentification"] = "1";
            return true;
        }
        else
        {
            return false;
        }
    }

    [WebMethod(EnableSession = true)]
    public bool Test()
    {
        if (Session["authentification"] != null && Session["authentification"].ToString() == "1")
        {
            return true;
        }
        else
        {
            return false;
        }
    }

先谢谢您，这个原理我了解了，但是针对我上面的动态调用Webservice方法，应该在哪里获取返回http头中的cookie内容呢？又该在哪里发送呢？劳驾再次指点一下吧，不胜感激。
请注意看我添加的注释
public partial class _Default : System.Web.UI.Page
   {
      protected void Page_Load(object sender,EventArgs e)
      {
         Response.Write("测试web服务,直接方法<br/>");
         CookieContainer container = new CookieContainer();
         localhost.Service1 service1 = new localhost.Service1();
         service1.CookieContainer = container;
         Response.Write(service1.Authenticate("raymond","raymond"));
         service1.CookieContainer = container;//如果这里不是下面的语句得到的仍然为False
         Response.Write(service1.Test());
         Response.Write("测试web服务,CodeDom方法<br/>");
         Response.Write(InvokeWebservice("http://localhost/MyTestWebService/Service1.asmx","MyTestWebService","Service1","Authenticate",new object[] { "raymond","raymond" },container));
         Response.Write(InvokeWebservice("http://localhost/MyTestWebService/Service1.asmx","Test",new object[] { },container));
      }

      public object InvokeWebservice(string url,object[] args,CookieContainer container)
      {
         try
         {
            System.Net.WebClient wc = new System.Net.WebClient();

            System.IO.Stream stream = wc.OpenRead(url + "?WSDL");

            System.Web.Services.Description.ServiceDescription sd
                = System.Web.Services.Description.ServiceDescription.Read(stream);

            System.Web.Services.Description.ServiceDescriptionImporter sdi
                = new System.Web.Services.Description.ServiceDescriptionImporter();

            sdi.AddServiceDescription(sd,ccu);
            if (true == cr.Errors.HasErrors)
            {
               System.Text.StringBuilder sb = new System.Text.StringBuilder();
               foreach (System.CodeDom.Compiler.CompilerError ce in cr.Errors)
               {
                  sb.Append(ce.ToString());
                  sb.Append(System.Environment.NewLine);
               }

               throw new Exception(sb.ToString());
            }

            System.Reflection.Assembly assembly = cr.CompiledAssembly;
            Type t = assembly.GetType(@namespace + "." + classname,true);
            object obj = Activator.CreateInstance(t);

            //设置CookieContainer 1987raymond添加
            PropertyInfo property = t.GetProperty("CookieContainer");
            property.SetValue(obj,container,null);

            System.Reflection.MethodInfo mi = t.GetMethod(methodname);
            return mi.Invoke(obj,args);
         }

         catch (Exception ex)
         {
            throw ex;
         }
      }
   }



执行结果
测试web服务,直接方法
TrueTrue测试web服务,CodeDom方法
TrueTrue