Web客户端使用下载文件，以抓住从服务器上的文件 - 处理异常

我有一个Web服务，其中我操纵POST和GET方法，以方便上传/下载功能，在客户机/服务器式建筑的一些文件。基本上，用户可以点击一个按钮来下载特定文件，使应用程序的一些变化，然后点击上传按钮把它送回来。

I have a web service in which I am manipulating POST and GET methods to facilitate upload / download functionality for some files in a client/server style architecture. Basically the user is able to click a button to download a specific file, make some changes in the app, then click upload button to send it back.

问题我有与下载。假设用户希望3个文件1.txt的，2.txt和3.txt。除了2.txt不存在于服务器上。

Problem I am having is with the download. Say the user expects 3 files 1.txt, 2.txt and 3.txt. Except 2.txt does not exist on the server.

所以，我有code等（在服务器端）：

So I have code like (on server side):

public class HttpHandler : IHttpHandler
{

    public void ProcessRequest
    {
       if (context.Request.HttpMethod == "GET")
       {
          GoGetIt(context)
       }
    }

private static void GoGetIt(HttpContext context)
{
     var fileInfoOfWhereTheFileShouldBe = new FileInfo(......);

     if (!fileInfoOfWhereTheFileShouldBe.RefreshExists())
     {
          //Remove this line below
          //throw new Exception("Oh dear the file doesn't exist");

          //Replace with a force return of whichever code I chose e.g. 200
          ??...
     }

    ...

所以，我的问题是，当我运行的应用程序，我用一个Web客户端上的客户端使用DownloadFile方法，然后使用code我在上面，我得到：

So the problem I have is that when I run the application, and I use a WebClient on client side to use DownloadFile method which then uses the code I have above, I get:

WebException是未处理：远程服务器返回错误：（500）内部服务器错误

WebException was unhandled: The remote server returned an error: (500) Internal Server Error.

（在调试）。如果我连接到浏览器，并使用的http：//本地主机：XXX / 1.txt的我可以通过服务器端code步骤和按计划抛出异常。所以我想我不知道我怎么可以处理在客户端内部服务器错误正确，所以我可以返回一些有意义的事情，如文件不存在。一个想法是使用周围的 WebClient.DownloadFile（地址，文件名）方法一试捕，但我不知道这就是将要发生的，即该文件没有按'唯一的错误牛逼存在。

(While debugging) If I attach to the browser and use http://localhost:xxx/1.txt I can step through server side code and throw the exception as intended. So I guess I'm wondering how I can handle the internal server error on the client side properly so I can return something meaningful like "File doesn't exist". One thought was to use a try catch around the WebClient.DownloadFile(address, filename) method but i'm not sure thats the only error that will occur i.e. the file doesn't exist.

编辑：该解决方案使用如下的Htt presponse

所以，如果我是用的Htt presponse，我能得到一些建议，如何开始？

So if I were to use HttpResponse, could I get some suggestions as how to start?

我删除从客户端的异常抛出，并更换定制的Htt presponse？所以基本上我想我会选择一个code使用，比如200，并迫使回报code 200，如果上述声明。见注释。

I remove the exception throw from the client side, and replace with custom HttpResponse? So basically I guess I would chose a code to use, say 200, and force return code 200 in that if statement above. See comment.

然后在客户端只需使用如果（Response.Status code == 200）和做任何我想做的事（通知用户文件不存在）

Then on client side just use If (Response.StatusCode == 200) and do whatever I want to do (inform user file doesn't exist )

我沿着正确的方向？

修改2：

我一直想用在我的文件拷贝方法尝试捕捉，然后在抓，设置状态code或状态的描述，但设置状态描述..这样的时候，这将引发异常：

I've been trying using a try catch around my file copy methods, then in the catch, setting the status code or status description but this throws exceptions when setting the status description.. like this:

context.Response.StatusDescription = ex.ToString();
context.Response.Status = ex.ToString();

ArgumentOutOfRangeException - 指定的参数已超出有效值范围的

ArgumentOutOfRangeException - specified argument was out of the range of valid values.