System.Web.UI.Control.RenderControl在从后台线程调用时失败

我有一个要求在后台线程中呈现控件并在邮件中发送输出。所以我有这段代码在后台线程中运行：System.Web.UI.Control.RenderControl在从后台线程调用时失败

System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(sendmail), new Object()); 
public void sendmail(object o) 
{ 
    UserControl cntrl = new Page().LoadControl("~/mycontrol.ascx") as UserControl; 
    StringWriter stringwriter = new StringWriter(); 
    Html32TextWriter htmlwriter = new Html32TextWriter(stringwriter); 
    cntrl.RenderControl(htmlwriter); 
    SendEmailUsingNetMail(stringwriter); 
} 

At runtime I am getting this exception 

System.NullReferenceException: Object reference NOT SET TO an instance of an object. 
AT System.Web.UI.HtmlControls.HtmlForm.GetActionAttribute() 
AT System.Web.UI.HtmlControls.HtmlForm.RenderAttributes(HtmlTextWriter writer) 
AT System.Web.UI.HtmlControls.HtmlControl.RenderBeginTag(HtmlTextWriter writer) 
AT System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) 
AT System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) 
AT System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
AT System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
AT System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) 
AT System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) 
AT System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) 
AT System.Web.UI.Control.Render(HtmlTextWriter writer) 
AT System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) 
AT System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) 
AT System.Web.UI.Control.RenderControl(HtmlTextWriter writer) 
AT RedBus.RBMail.sendmail(object o)

从asp.net请求的线程中运行时相同的代码工作完全正常。是否有可能让这个东西在后台线程本身工作？如果是的话如何？

感谢，普拉丹

来源

2013-01-08 pradhanbv

添加表单到您的网页：

System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(sendmail), new Object()); 
public void sendmail(object o) 
{ 

    System.Web.UI.Page() pageHolder = new System.Web.UI.Page() 
       {AppRelativeTemplateSourceDirectory = HttpRuntime.AppDomainAppVirtualPath }; 
    System.Web.UI.HtmlControls.HtmlForm form = new System.Web.UI.HtmlControls.HtmlForm(); 
    UserControl cntrl = new Page().LoadControl("~/mycontrol.ascx") as UserControl; 
    form.Controls.Add(cntrl); 
    pageHolder.Controls.Add(form); 

    StringWriter stringwriter = new StringWriter(); 

    HttpContext.Current.Server.Execute(pageHolder, stringwriter, false); 
    SendEmailUsingNetMail(stringwriter); 
}

而且，我写了一个开放源码软件项目做这个叫ucajax，的lib是为了与Web服务消费，但没有理由不能直接调用方法来呈现控件。

来源

2013-01-08 13:28:19

我不使用会话。 – pradhanbv

忽略会话请参阅更新 –

行HttpContext.Current.Server.Execute（pageHolder，stringwriter，false）;由于HttpContext.Current为空，所以会引发空引用异常。 – pradhanbv

System.Web.UI.Control.RenderControl在从后台线程调用时失败

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