在这篇文章中。WCF扮演server，向外提供LoginVaild服务。Silverlight扮演client。调用WCF提供的LoginVaild服务。思路有了。以下进行代码实现。

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')

WCFserver实现

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

  [OperationContract]

        bool LoginVaild(string userName, string password);

2.加入ADO.Net实体数据模型文件--Model.edmx。用于对数据表T_User的訪问。

3.在Service1.svc中对LoginVaild方法进行实现：

 public bool LoginVaild(string userName, string password)

        {

            bool result = false;

            //须要訪问的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;

        }

4.在项目的根文件夹加入跨域訪问文件clientaccesspolicy.xml。内容例如以下：

<?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WCFserver使用特定port进行訪问，方法：选中WCFserver项目-->邮件属性-->Web-->特定port，输入1316。这样保证我们每次能够通过1316port訪问WCF提供的服务。

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

Silverlightclient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();

        }