HtmlAnchor.RenderControl引发NullReference异常

Question

我这里有一段代码

   var anchor = new HtmlAnchor {HRef = temp, InnerText = this.LinkDescription};
            anchor.Attributes.Add("class", "navActive back");
            anchor.ServerClick += new EventHandler(AnchorServerClick);
            writer.Write("<div id=\"leftnav\"><ul><li>");
            anchor.RenderControl(writer);
            writer.Write("</li></ul></div>");

在自定义web控件内。我在anchor.RenderControl得到了一个nullReference异常，为什么？我调试了上面的代码，编写器也不是空的，锚也是。那是怎么回事？谢谢!

编辑:我添加堆栈跟踪是为了调试

[NullReferenceException: Object reference not set to an instance of an object.]
System.Web.UI.HtmlControls.HtmlAnchor.GetPostBackOptions() +107
System.Web.UI.HtmlControls.HtmlAnchor.RenderAttributes(HtmlTextWriter writer) +10975634
System.Web.UI.HtmlControls.HtmlControl.RenderBeginTag(HtmlTextWriter writer) +56
System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +26
CER.Portal.Dashboard.Controls.BackLink.Render(HtmlTextWriter writer) +1151

Answer 1

查看GetPostBackOptions方法的代码，您需要将page属性设置为当前页面，或者将CausesValidation属性设置为false：

private PostBackOptions GetPostBackOptions()
{
   PostBackOptions options = new PostBackOptions(this, string.Empty) 
   {
      RequiresJavaScriptProtocol = true
   };
   if (this.CausesValidation && (this.Page.GetValidators(this.ValidationGroup).Count > 0))
   {
      options.PerformValidation = true;
      options.ValidationGroup = this.ValidationGroup;
   }
   return options;
}

在RenderControl调用前添加anchor.Page = this.Page或anchor.CausesValidation = false。