VB.NET: Download executable file from Dropbox

[Stephen_Hawking]

Hello everyone,
I have some issues with my vb code.
What I'm trying to do is: Download an .exe file from dropbox.
When it has finished to download the file weighs 0 bytes

My code:

  Using client = New System.Net.WebClient
            client.DownloadFileAsync(New Uri("https://www.dropbox.com/s/ddsavgmfwvjqgtr/testfile.exe?dl=1"), "C:\test.exe")
        End Using

Does someone know what I wrote wrong ?

Thanks in advance!