Error Occurs when uploading a file to FTP server

Protected Sub btnUpload_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnUpload.Click
    Try
        Dim filePath As String = "~/"
        Dim fileName As String = fileUpload.FileName.ToString()
        fileUpload.SaveAs(Server.MapPath(filePath) & fileName)
        ErrorMessage.Text = "Uploaded Successfully :)"
    Catch ex As Exception
        ErrorMessage.Text = ex.Message.ToString()
    End Try