Download file in vb either in unknown format or damaged ? help

Imports System.Net
Public Class Form1
    Private WithEvents httpclient As WebClient
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Button1.Enabled = False
        httpclient = New WebClient
        AddHandler httpclient.DownloadFileCompleted, AddressOf Downloaded
        httpclient.DownloadFileAsync(New Uri("https://www.download source.com/call.zip"), ("C:\download\call.zip"))
    End Sub
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        persent.Text = ""
    End Sub
 
    Private Sub dpc(ByVal sender As Object, ByVal e As System.Net.DownloadProgressChangedEventArgs) Handles httpclient.DownloadProgressChanged
        persent.Text = e.ProgressPercentage
    End Sub
 
    Private Sub Downloaded()
        If System.IO.File.Exists("C:\download\call.zip") = True Then
            Process.Start("C:\download\call.zip")
        Else
            MsgBox("Doesn't exist", 64, "Open")
        End If
    End Sub
End Class