/ </summary>
[DefaultProperty("Text"),
ToolboxData("<{0}:PopupGreeting runat=server></{0}:PopupGreeting>")]
public class PopupGreeting : System.Web.UI.Control
{
[Bindable(true),
Category("Appearance"),
DefaultValue("")]
public string PopupMessage
{
get
{
// 检查 ViewState 中是否存在该项目
object popupMessage = this.ViewState["PopupMessage"];
if (popupMessage != null)
return this.ViewState["PopupMessage"].ToString();
else
return "Welcome to my Web site!";
}
set
{
// 指定 ViewState 变量
ViewState["PopupMessage"] = value;
}
}
[Bindable(true),
Category("Appearance"),
DefaultValue("")]
public bool Enabled
{
get
{
// 检查 ViewState 中是否存在该项目
object enabled = this.ViewState["Enabled"];
if (enabled != null)
return (bool) this.ViewState["Enabled"];
else
return true;
}
set
{
// 指定 ViewState 变量
ViewState["Enabled"] = value;
}
}
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
string scriptKey = "intoPopupMessage:" + this.UniqueID;
if (!Page.IsStartupScriptRegistered(scriptKey) && this.Enabled &&
!Page.IsPostBack)
{
string scriptBlock =
@"<script language=""JavaScript"">
<!--
alert(""%%POPUP_MESSAGE%%"");
// -->
</script>";
scriptBlock = scriptBlock.Replace("%%POPUP_MESSAGE%%", this.PopupMessage);
Page.RegisterStartupScript(scriptKey, scriptBlock);
}
}
}
}
请记住下面两件事：首先，Enabled 和 PopupMessage 属性保存在 ViewState 中，这样在回传时这些值可以始终保持一致; 其次，在 OnPreRender() 方法中，用于脚本块的关键字是文本 intoPopupMessage: 加上控件的 UniqueID 属性。如果
