将视图渲染为字符串，然后重定向会导致异常

发布于 2024-07-27 04:32:38 字数 1988 浏览 13 评论 0原文

所以问题是：我正在通过将完整视图页面渲染为字符串并发送它们来构建要由我的应用程序发送的电子邮件。只要我之后不重定向到该网站上的另一个 URL，此操作就不会出现任何问题。每当我尝试时，都会收到“System.Web.HttpException：发送 HTTP 标头后无法重定向”。

我相信问题来自于我正在重用来自创建电子邮件的调用的控制器操作的上下文。更具体地说，来自上下文的 HttpResponse。不幸的是，我无法创建一个使用 HttpWriter 的新 HttpResponse，因为该类的构造函数无法访问，并且使用从 TextWriter 派生的任何其他类都会导致 response.Flush() 本身引发异常。

有人有解决方案吗？

    public static string RenderViewToString(
        ControllerContext controllerContext,
        string viewPath,
        string masterPath,
        ViewDataDictionary viewData,
        TempDataDictionary tempData)
    {
        Stream filter = null;
        ViewPage viewPage = new ViewPage();

        //Right, create our view
        viewPage.ViewContext = new ViewContext(controllerContext,
            new WebFormView(viewPath, masterPath), viewData, tempData);

        //Get the response context, flush it and get the response filter.
        var response = viewPage.ViewContext.HttpContext.Response;
        //var response = new HttpResponseWrapper(new HttpResponse
        //    (**TextWriter Goes Here**));
        response.Flush();
        var oldFilter = response.Filter;

        try
        {
            //Put a new filter into the response
            filter = new MemoryStream();
            response.Filter = filter;

            //Now render the view into the memorystream and flush the response
            viewPage.ViewContext.View.Render(viewPage.ViewContext,
                viewPage.ViewContext.HttpContext.Response.Output);
            response.Flush();

            //Now read the rendered view.
            filter.Position = 0;
            var reader = new StreamReader(filter, response.ContentEncoding);
            return reader.ReadToEnd();
        }
        finally
        {
            //Clean up.
            if (filter != null)
                filter.Dispose();

            //Now replace the response filter
            response.Filter = oldFilter;
        }
    }

原文

So here's the issue: I'm building e-mails to be sent by my application by rendering full view pages to strings and sending them. This works without any problem so long as I'm not redirecting to another URL on the site afterwards. Whenever I try, I get "System.Web.HttpException: Cannot redirect after HTTP headers have been sent."

I believe the problem comes from the fact I'm reusing the context from the controller action where the call for creating the e-mail comes from. More specifically, the HttpResponse from the context. Unfortunately, I can't create a new HttpResponse that makes use of HttpWriter because the constructor of that class is unreachable, and using any other class derived from TextWriter causes response.Flush() to throw an exception, itself.

Does anyone have a solution for this?

    public static string RenderViewToString(
        ControllerContext controllerContext,
        string viewPath,
        string masterPath,
        ViewDataDictionary viewData,
        TempDataDictionary tempData)
    {
        Stream filter = null;
        ViewPage viewPage = new ViewPage();

        //Right, create our view
        viewPage.ViewContext = new ViewContext(controllerContext,
            new WebFormView(viewPath, masterPath), viewData, tempData);

        //Get the response context, flush it and get the response filter.
        var response = viewPage.ViewContext.HttpContext.Response;
        //var response = new HttpResponseWrapper(new HttpResponse
        //    (**TextWriter Goes Here**));
        response.Flush();
        var oldFilter = response.Filter;

        try
        {
            //Put a new filter into the response
            filter = new MemoryStream();
            response.Filter = filter;

            //Now render the view into the memorystream and flush the response
            viewPage.ViewContext.View.Render(viewPage.ViewContext,
                viewPage.ViewContext.HttpContext.Response.Output);
            response.Flush();

            //Now read the rendered view.
            filter.Position = 0;
            var reader = new StreamReader(filter, response.ContentEncoding);
            return reader.ReadToEnd();
        }
        finally
        {
            //Clean up.
            if (filter != null)
                filter.Dispose();

            //Now replace the response filter
            response.Filter = oldFilter;
        }
    }

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