Dear Canh
I didn't foloow the thread from the start, but if you're using MAPI, try the following code, instead of what you use:

this.parent.OleMMess.compose
THIS.PARENT.OleMMess.recipdisplayname=this.Parent.c_nguoinhan
this.parent.OleMMess.msgnotetext=this.Parent.c_noidungthu
this.parent.OleMMess.msgsubject=this.Parent.c_chudethu
this.parent.OleMMess.AttachmentIndex = 0
this.parent.OleMMess.AttachmentType = 0
this.parent.OleMMess.AttachmentName = "ADD.TXT"
this.parent.OleMMess.AttachmentPathName = "d:\dtd40x\add.txt"

HTH
Jaime

>I tried, but it does not work.
>Here codes:
>

this.parent.OleMMess.compose
>THIS.PARENT.OleMMess.recipdisplayname=this.Parent.c_nguoinhan
>this.parent.OleMMess.msgnotetext=this.Parent.c_noidungthu
>this.parent.OleMMess.msgsubject=this.Parent.c_chudethu
>this.parent.OleMMess.Attachments.Add("ADD.TXT",0,1,"d:\dtd40x\ADD.TXT")

>
>I get a message error following:
>
>

Member Attachments does not evaluate to an object.

>&&Press OK button, get other message
>

OLE Idispatch exception code 0 from MAPIMessages: Invalid session.