我试图在我的方法中的函数失败时抛出一个异常，到目前为止，我的代码如下：

if (sourceFile.Exists)
            // Would be nice to add ticker / spinner, while the file header on the remote server is being read!!
            {
                var request = (HttpWebRequest)WebRequest.Create(@"http://google.com/test.zip");
                request.Method = "HEAD";
                var response = (HttpWebResponse)request.GetResponse();

                if (response.LastModified > sourceFile.LastWriteTime)
                {

                    Download_Click(sender, e);

                    // use response.GetStream() to download the file.
                }