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)
{
System.Windows.Browser.HtmlPage.Window.Invoke(“callWebService”, null);
}　　

　　关于JavaScript的调用可以参照一下内容：

　　通过ScriptServiceAttribute添加

[ScriptService]
public class UserValidationService: System.Web.Services.WebService
{
    [WebMethod]
    public bool ValidateUserName(string strInput)
    {
        return !GetUserByUserName(strInput); //If user exists return false indicates the name is no longer availabe.
    }

    private bool GetUserByUserName(string strUserName)
    {
         bool blnIsUserExists = false;        
         //Call database API to see if the username is availabe, set blnIsUserExists to true if exists.
         return blnIsUserExists;
    }
}　　

　　通过页面添加ScriptMananger控件

<asp:ScriptManager runat=”server” ID=”scriptManagerId”>
                <Services>
                    <asp:ServiceReference  Path=”UserValidationService.asmx” />
                </Services>
</asp:ScriptManager>　　

　　像调用JavaScript局部函数一样调用Webservice

<script type=”text/javascript”>
function validateUserName()
{
  var userName = document.getElementById(“txtUserName”).value;
UserValidationService.ValidateUserName(userName,showValidateResult,validateUserNameError);

}
function validateUserNameError(result)
{
    //Do nothing if any error, ideally, we should log this error to database.
}

function showValidateResult(result)
{
//Since it is only a boolean value, no need to get result.d, if result contains .net object,
// use result.length and result.d to retrieve the object.
    if(!result)
    {   
        //Not available
    }else
    {
        //Username is still available
    }
}
</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。

using MySilver.MyService;
……
…..

private void btnSend_Click(object sender, RoutedEventArgs e)
{
         if (!String.IsNullOrEmpty(txtMessage.Text.Trim()))
         {
               lstHisotryMessage.Items.Add(“Gene: ” + txtMessage.Text.Trim());
               GeneMessage message = new GeneMessage();
               message.Body = txtMessage.Text.Trim();
               MyServiceclient = new MyService();
               client.SendMessageCompleted += new EventHandler<SendMessageCompletedEventArgs>(client_SendMessageCompleted);
               client.SendMessageAsync(message);
         }
         else
         {
               MessageBox.Show(“You cannot send empty message!”);
         }
}

protected void client_SendMessageCompleted(object sender, SendMessageCompletedEventArgs e)
{
         txtMessage.Text = e.Result.MessageID.ToString();
}