在这篇文章中，WCF扮演服务器，向外提供LoginVaild服务；Silverlight扮演客户端，调用WCF提供的LoginVaild服务。思路有了，下面进行代码实现。

  数据库脚本实现

USE [test]
GO
/****** Object:  Table [dbo].[T_User]    Script Date: 09/28/2014 21:12:02 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[T_User](
	[username] [varchar](20) NOT NULL,
	[password] [varchar](20) NOT NULL,
 CONSTRAINT [PK_T_User] PRIMARY KEY CLUSTERED 
(
	[username] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
INSERT [dbo].[T_User] ([username], [password]) VALUES (N'admin', N'admin')

  WCF服务器实现

  1.新建一个WCF服务库项目，在默认生成的IServer1.cs接口在添加LoginVaild服务的声明：

  [OperationContract]
        bool LoginVaild(string userName, string password);

   3.在Service1.svc中对LoginVaild方法进行实现：

 public bool LoginVaild(string userName, string password)
        {
            bool result = false;
            //需要访问的ADO.Net数据实体模型
            using (SLtestEntitiesSecond entities = new SLtestEntitiesSecond())
            {
                var user = entities.T_User.Where(c => c.username == userName && c.password == password).SingleOrDefault();
                if (user == null)
                {
                    result = false;
                }
                else
                {
                    result = true;
                }

            }
            return result;
        }

<?xml version="1.0" encoding="utf-8" ?>
<access-policy>
  <cross-domain-access>
    <policy>
      <allow-from http-request-headers="*">
        <domain uri="*"/>   
      </allow-from>
      <grant-to>
        <resource path="/" include-subpaths="true"/>
      </grant-to>    
    </policy> 
  </cross-domain-access>
</access-policy>

  5.设定WCF服务器使用特定端口进行访问，方法：选中WCF服务器项目-->邮件属性-->Web-->特定端口，输入1316。这样保证我们每次可以通过1316端口访问WCF提供的服务。

  到此，WCF服务器端配置完成，选中Service1.svc文件，在浏览器中浏览器下WCF提供的服务。

  Silverlight客户端实现

    private void button1_Click(object sender, RoutedEventArgs e)
        {
            string userName = txtusername.Text.Trim();
            string password = txtpassword.Text.Trim();
            Service1Client client = new Service1Client();
            client.LoginVaildCompleted += new EventHandler<LoginVaildCompletedEventArgs>(client_LoginVaildCompleted);
            client.LoginVaildAsync(userName, password);
            client.CloseAsync();
        }

        void client_LoginVaildCompleted(object sender, LoginVaildCompletedEventArgs e)
        {
            if (e.Error == null)
            {
                //MessageBox.Show(e.Result.ToString());
                if (e.Result == true)
                {
                    this.Content = new MainPage();

                }
                else
                {
                    MessageBox.Show("用户名或密码错误!");
                }
            }
            else
            {
                MessageBox.Show(e.Error.ToString());
            }
        }

  private void Application_Startup(object sender, StartupEventArgs e)
        {
            this.RootVisual = new Login();
        }

Silverlight+WCF实现跨域调用

原文：http://blog.csdn.net/quwenzhe/article/details/39646885