使用C＃ASP.NET时，“WebClient请求期间发生异常”

Question

So, I have built an auto update program to my program.

The code that is running in here is:

new WebClient().DownloadFile("XXXX", checkingfolder.SelectedPath);

the XXX is my webserver that is running as a VPS server in verio, with the newest IIS and everything.

When the user clicks on the download button, it says:

'An exception occurred during a WebClient request.

The thing is, that I dont even know why - i am just doing try catch.

Anyone here have any idea why this happened?

Thanks for any help you will give me, you have no idea how much you are helping me here - thanks again !

Answer 1

I can reproduce this if I specify, as seems to be the case in your example, a folder name rather than a file name the destination. Supply a file name instead.

As an aside; if I look at the InnerException , it tells me that the problem relates to the file path:

using(var client = new WebClient())
{
    try
    {
        client.DownloadFile(
            "http://stackoverflow.com/questions/8033619/an-exception-occurred-durning-a-webclient-request-c-sharp-asp-net/8033687#8033687",
            @"j:\MyPath");
    }
    catch (Exception ex)
    {
        while (ex != null)
        {
            Console.WriteLine(ex.Message);
            ex = ex.InnerException;
        }
    }
}

Which gives:

An exception occurred during a WebClient request.
Access to the path 'j:\MyPath' is denied.

If I change it to a file , it works fine:

client.DownloadFile(
    "http://stackoverflow.com/questions/8033619/an-exception-occurred-durning-a-webclient-request-c-sharp-asp-net/8033687#8033687",
    @"j:\MyPath\a.html");

Answer 2

有时，当另一个类或进程正在访问您刚刚下载的文件时，可能会发生此错误

Answer 3

it gives exception, if directory to path does not exist.

for example path is @"j:\\Folder\\SubFolder\\123.pdf and SubFolder does not exist ,it will throw exception.

Answer 4

I ran into this error when I was trying to download a file, where the resulting downloaded file path would have been longer than some arbitrary limit

After changing the downloaded file's path name to be 250 characters long, the problem went away

Answer 5

Beside other answers, beware that the same WebException might also occur if the client process does not have needed permission to create output file.

I would suggest you to take the following strategy:

1. Download file to a unique filename with .tmp ( .txt ) extensions Windows Temporary Folder to avoid write-permission and other permissions issues
2. Move temporary file to destination folder
3. Rename temporary file to destination filename

Hope it helps :-)

Answer 6

If Directory does not exist,this error message comes as 'An exception occurred during a WebClient request" Because Web Client Does not find the Folder to store downloaded files.

Hope it Helps-:)