Downloading .docx file in asp.net is being corrupted after download.

If e.CommandName = "Download" Then
           Dim fst As New FileStream(Server.MapPath(e.CommandArgument), FileMode.Open)
           Dim fl As String = e.CommandArgument
           Dim file As String() = e.CommandArgument.ToString.Split(".")
           Dim extension As String = file(file.Length - 1)
           Dim bytBytes(fst.Length) As Byte
           'read file byte by byte
           fst.Read(bytBytes, 0, fst.Length)
           fst.Close()
           Response.AddHeader("Content-disposition", "attachment; filename=" & fl)

           If extension = "docx" Then
               Response.ContentType = "application/vnd.ms-word.document"
           ElseIf extension = "pdf" Then
               Response.ContentType = "Application/pdf"
           ElseIf extension = "xls" Then
               Response.ContentType = "application/vnd.ms-excel"
           ElseIf extension = "xlsx" Then
               Response.ContentType = "application/vnd.ms-excel"
           ElseIf extension = "doc" Then
               Response.ContentType = "application/ms-word"
           End If


           'write all the byte to newly created file
           Response.BinaryWrite(bytBytes)
           Response.End()
       End If