Android Question Playing IMEI from device in .txt file

Good night I want to do the following, I'm getting IMEI from the device and playing on the label I want to generate a .txt file with the device IMEI example: BY900f4g7G.txt I am using this code to generate the .txt:

Lbl_IMEI.Text = GetDeviceId

Lbl_IMEI.Tag = "lbl_IMEI"


TextWriter1.Initialize (File.OpenOutput
(File.DirDefaultExternal, $ "$ {Lbl_IMEI.Tag} .txt" $, False))

It compiles more the .txt file has the name Lbl_IMEI.txt, how do I get the IMEI from the device ?? (BY900f4g7G.txt)
Does anyone have an example ??