webpart中动态调用webservice出错,该怎么解决

        public static string[] GetWeatherbyCityName(string cityName)
        {
            String[] item = null;

            SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                WebClient client = new WebClient();
                client.Proxy = new WebProxy("10.0.15.29", 8080);
                client.Proxy.Credentials = System.Net.CredentialCache.DefaultCredentials;
                String url = "http://www.webxml.com.cn/WebServices/WeatherWebService.asmx?wsdl";//这个地址可以写在Config文件里面，这里取出来就行了.在原地址后面加上： ?WSDL

                Stream stream = client.OpenRead(url);
                ServiceDescription description = ServiceDescription.Read(stream);

                ServiceDescriptionImporter importer = new ServiceDescriptionImporter();//创建客户端代理代理类。

                importer.ProtocolName = "Soap"; //指定访问协议。
                importer.Style = ServiceDescriptionImportStyle.Client; //生成客户端代理。
                importer.CodeGenerationOptions = CodeGenerationOptions.GenerateProperties | CodeGenerationOptions.GenerateNewAsync;

                importer.AddServiceDescription(description, null, null); //添加WSDL文档。

                CodeNamespace nmspace = new CodeNamespace(); //命名空间
                nmspace.Name = "TestWebService";
                CodeCompileUnit unit = new CodeCompileUnit();
                unit.Namespaces.Add(nmspace);

                ServiceDescriptionImportWarnings warning = importer.Import(nmspace, unit);
                CodeDomProvider provider = CodeDomProvider.CreateProvider("CSharp");

                CompilerParameters parameter = new CompilerParameters();
                parameter.GenerateExecutable = false;
                parameter.OutputAssembly = @"C:\Inetpub\wwwroot\wss\VirtualDirectories\80\bin\MyTest.dll";//输出程序集的名称
                parameter.ReferencedAssemblies.Add("System.dll");
                parameter.ReferencedAssemblies.Add("System.XML.dll");
                parameter.ReferencedAssemblies.Add("System.Web.Services.dll");
                parameter.ReferencedAssemblies.Add("System.Data.dll");

                CompilerResults result = provider.CompileAssemblyFromDom(parameter, unit);
                if (result.Errors.HasErrors)
                {
                    // 显示编译错误信息
                }

                Assembly asm = Assembly.LoadFrom(@"C:\Inetpub\wwwroot\wss\VirtualDirectories\80\bin\MyTest.dll");//加载前面生成的程序集
                Type t = asm.GetType("TestWebService.WeatherWebService");
                object o = Activator.CreateInstance(t);
                MethodInfo method = t.GetMethod("getWeatherbyCityName");//GetPersons是服务端的方法名称,你想调用服务端的什么方法都可以在这里改,最好封装一下

                ////上面是根据WebService地址，模似生成一个代理类,如果你想看看生成的代码文件是什么样子，可以用以下代码保存下来，默认是保存在bin目录下面
                //TextWriter writer = File.CreateText("MyTest.cs");
                //provider.GenerateCodeFromCompileUnit(unit, writer, null);
                //writer.Flush();
                //writer.Close();

                string[] parameters = new string[] { cityName };//这个就是构造参数的
                item = (String[])method.Invoke(o, parameters);
                //注：method.Invoke(o, null)返回的是一个Object,如果你服务端返回的是DataSet,这里也是用(DataSet)method.Invoke(o, null)转一下就行了

            });
            return item;
        }

     protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
               string[] _weatherArray = WeatherHelp.GetWeatherbyCityName("上海");
            }
        }