使用控制器操作过滤器捕获 HTML 输出

本文介绍了使用控制器操作过滤器捕获 HTML 输出的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我在一个动作上设置了以下过滤器来捕获 HTML 输出，将其转换为字符串，执行一些操作来修改字符串，并返回一个带有新字符串的 ContentResult.不幸的是，我一直以空字符串结尾.

I've got the following filter in place on an action to capture the HTML output, convert it to a string, do some operations to modify the string, and return a ContentResult with the new string. Unfortunately, I keep ending up with an empty string.

private class UpdateFilter : ActionFilterAttribute { private Stream stream; public override void OnActionExecuting(ActionExecutingContext filterContext) { stream = filterContext.HttpContext.Response.Filter; stream = new MemoryStream(); filterContext.HttpContext.Response.Filter = stream; } public override void OnResultExecuted(ResultExecutedContext filterContext) { StreamReader responsereader = new StreamReader(filterContext.HttpContext.Response.Filter); //empty stream? why? responsereader.BaseStream.Position = 0; string response = responsereader.ReadToEnd(); ContentResult contres = new ContentResult(); contres.Content = response; filterContext.Result = contres; } }

我确定 StreamReader(stream).ReadToEnd() 返回一个空字符串，但我不知道为什么.

I've pinned down that StreamReader(stream).ReadToEnd() returns an empty string, but I can't figure out why.

有什么想法可以解决这个问题吗?

Any ideas how to fix this?

EDIT:我把OnActionExecuted改成了OnResultExecuted，现在View生成后调用了，但是流还是空的！

EDIT: I've changed the OnActionExecuted to OnResultExecuted, and now it is called after the View has been generated, but the stream is still empty!

推荐答案

我通过劫持 HttpWriter 解决了这个问题，并将其写入 StringBuilder 而不是响应，然后做任何需要的事情在将响应写入输出之前对其进行/处理.

I solved this by hijacking the HttpWriter, and having it write into a StringBuilder rather than the response, and then doing whatever needs to be done to/with the response before writing it to the output.

private class UpdateFilter : ActionFilterAttribute { private HtmlTextWriter tw; private StringWriter sw; private StringBuilder sb; private HttpWriter output; public override void OnActionExecuting(ActionExecutingContext filterContext) { sb = new StringBuilder(); sw = new StringWriter(sb); tw = new HtmlTextWriter(sw); output = (HttpWriter)filterContext.RequestContext.HttpContext.Response.Output; filterContext.RequestContext.HttpContext.Response.Output = tw; } public override void OnResultExecuted(ResultExecutedContext filterContext) { string response = sb.ToString(); //response processing output.Write(response); } }

使用 HttpContext 避免线程错误的上述代码 - 参见 jaminto 的评论

Above code using the HttpContext to avoid threading errors - see jaminto's comment

private class RenderFilter : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { StringBuilder sb = new StringBuilder(); StringWriter sw = new StringWriter(sb); HtmlTextWriter tw = new HtmlTextWriter(sw); HttpWriter output = (HttpWriter)filterContext.RequestContext.HttpContext.Response.Output; filterContext.HttpContext.Items["sb"] = sb; filterContext.HttpContext.Items["output"] = output; filterContext.RequestContext.HttpContext.Response.Output = tw; } public override void OnResultExecuted(ResultExecutedContext filterContext) { string response = filterContext.HttpContext.Items["sb"].ToString(); //response processing ((HttpWriter)filterContext.HttpContext.Items["output"]).Write(response); } }