Why WebClient.DownloadProgressChanged is fired only when download is completed?

[FLASHCODER]

I'm trying show the download progress step by step according with each byte is download, but my WebClient.DownloadProgressChanged is fired only when download is completed. How solve it?

Private WithEvents myWebClient As New WebClient
Dim installPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), Environment.MachineName)

Private Sub Installer_KeyDown(sender As Object, e As KeyEventArgs) Handles MyBase.KeyDown
e.SuppressKeyPress = (e.Alt AndAlso e.KeyCode = Keys.F4)
End Sub

Private Sub Installer_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown

If Not Directory.Exists(installPath) Then

Directory.CreateDirectory(installPath)

End If

myWebClient = New WebClient
myWebClient.DownloadFileAsync(New Uri("https://site.com/myfile.zip"), Path.Combine(installPath, "myfile.zip"))

End Sub

Dim dTotalToDownloadMB As Decimal
Dim dDownloadProgress As Decimal
Dim dDownloadedMB As Decimal

Public Sub myWebClient_DownloadProgressChanged(ByVal sender As Object, ByVal e As System.Net.DownloadProgressChangedEventArgs) Handles myWebClient.DownloadProgressChanged
Try
dDownloadProgress = CStr(e.BytesReceived / e.TotalBytesToReceive * 100)
Progresso.Value = CInt(dDownloadProgress)
dDownloadedMB = Format((e.BytesReceived / 1024) / 1024, "###,###,##0.00")
dTotalToDownloadMB = Format((e.TotalBytesToReceive / 1024) / 1024, "###,###,##0.00")
Me.Text = "Downloaded: " & dDownloadedMB & "MB out of " & dTotalToDownloadMB & "MB - Progress: " _
& Format(dDownloadProgress, "###.00") & "%"
Catch ex As Exception
End Try
End Sub

Private Sub myWebClient_DownloadFileCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.AsyncCompletedEventArgs) Handles myWebClient.DownloadFileCompleted
MsgBox("Download Completed", MsgBoxStyle.Information)
End Sub

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