WebClient not downloading full file?

Question

I have a WebClient downloading a .chm file (as seen in the code below). It seems to be very irregular in what it is downloading. The full file size is around 2500-2600 KB but about 50-75% of the time I get files back that are smaller (some examples: 1233 KB, 657 KB, 353 KB, 1745 KB, etc.).
(Code is simplified/personal details removed)

public static void DownloadMyFile(string destFileAndPath)
{
    //Get base for help Url, stop at first "/" ignoring "https://", then add path in server
    string Url = "https://mywebservice.com/myFile.chm";

    using (var client = new WebClient())
    {
        //I need to do stuff to the downloaded file when done
        client.DownloadFileCompleted += client_DownloadFileCompleted;

        client.DownloadFileAsync(new Uri(Url), destFileAndPath);

        //More waiting?
        while (client.IsBusy) { }
    }
}

And the Event, which is working fine, but on an "unfinished" file:

public static void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
    //Do stuff like comparing the file to another, renaming, copying, etc.
}  

Am I really missing something here?

Answer 1

It looks like Paul Roub's comment led me to the correct solution. I was only checking against the e.Cancelled property.

Occasionally, there were exceptions thrown (mostly a WebException of some kind) that would cause the download to error. Once I checked the e.Error property, I was able to either retry or handle the failure for my situation.