实现Silverlight 与数据库交互的途径

基于安全原因的考虑，Silverlight是不允许直接访问数据库的。但还是有很多方法来间接实现Silverlight对数据库的访问。比如以下的三种方式：1 RESTful API；2 在Silverlight下借助JavaScript来实现访问数据库；3 利用.NET Web服务模板——Silverlight-enabled。本文将主要介绍一下后俩种方法。

利用JavaScript实现Silverlight与数据库的交互

只要在Silverlight事件处理的后面添加调用以下简单的JavaScript代码即可。其中”callWebService”是JavaScript的函数。

 

 protected void btnSubmit(object sender,EventArgs e)
2 {
3 System.Windows.Browser.HtmlPage.Window.Invoke("callWebService", null);
4 }

　　关于JavaScript的调用可以参照一下内容：

　　通过ScriptServiceAttribute添加

 1 [ScriptService]
 2 public class UserValidationService: System.Web.Services.WebService
 3 {
 4     [WebMethod]
 5     public bool ValidateUserName(string strInput)
 6     {
 7         return !GetUserByUserName(strInput); //If user exists return false indicates the name is no longer availabe.
 8     }
 9 
10     private bool GetUserByUserName(string strUserName)
11     {
12          bool blnIsUserExists = false;         
13          //Call database API to see if the username is availabe, set blnIsUserExists to true if exists.
14          return blnIsUserExists;
15     }
16 }

 

通过页面添加ScriptMananger控件

 

 <asp:ScriptManager runat="server" ID="scriptManagerId">
2                 <Services>
3                     <asp:ServiceReference  Path="UserValidationService.asmx" />
4                 </Services>
5 </asp:ScriptManager>

 

 

像调用JavaScript局部函数一样调用Webservice

 

 1 <script type="text/javascript">
 2 function validateUserName()
 3 {
 4   var userName = document.getElementById("txtUserName").value;
 5 UserValidationService.ValidateUserName(userName,showValidateResult,validateUserNameError);
 6 
 7 } 
 8 function validateUserNameError(result)
 9 {
10     //Do nothing if any error, ideally, we should log this error to database.
11 }
12 
13 function showValidateResult(result)
14 {
15 //Since it is only a boolean value, no need to get result.d, if result contains .net object,
16 // use result.length and result.d to retrieve the object.
17     if(!result)
18     {    
19         //Not available
20     }else
21     {
22         //Username is still available
23     }
24 }
25 </script>

 

　利用Silverlight-enabled Webservice实现Silverlight与数据库的交互

　　首先通过模板创建一个Silverlight-enabled Webservice，然后将数据库和其他Server-related添加到服务里。接下来，将此服务添加引用到Silverlight 应用中。最后利用如下代码从Silverlight 应用中调用webservice。

 

 

 1 using MySilver.MyService;
 2 ......
 3 .....
 4 
 5 private void btnSend_Click(object sender, RoutedEventArgs e)
 6 {
 7          if (!String.IsNullOrEmpty(txtMessage.Text.Trim())) 
 8          {
 9                lstHisotryMessage.Items.Add("Gene: " + txtMessage.Text.Trim()); 
10                GeneMessage message = new GeneMessage(); 
11                message.Body = txtMessage.Text.Trim();
12                MyServiceclient = new MyService(); 
13                client.SendMessageCompleted += new EventHandler<SendMessageCompletedEventArgs>(client_SendMessageCompleted); 
14                client.SendMessageAsync(message);
15          }
16          else
17          {
18                MessageBox.Show("You cannot send empty message!"); 
19          }
20 }
21 
22 protected void client_SendMessageCompleted(object sender, SendMessageCompletedEventArgs e)
23 {
24          txtMessage.Text = e.Result.MessageID.ToString();
25 }

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