/// <summary>
/// 重载OnPreRender，输出ClientStateField，注册控件，注册Css文件
/// Fires the PreRender event
/// </summary>
/// <param name="e">事件参数</param>
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
EnsureID();
// EnsureScriptManager();
if (SupportsClientState)
{
Page.ClientScript.RegisterHiddenField(ClientStateFieldID, SaveClientState());
Page.RegisterRequiresPostBack(this);
}
ScriptManager.RegisterScriptControl <ScriptControlBase>(this);
ScriptObjectBuilder.RegisterCssReferences(this);
}