Forms :: Make A Log .txt File From TextBox?

how i can make VB to write the data from my textbox to a .txt , making it a log. The thing is my textbox is multiline, but when i log the data to the .txt it perfectly works BUT it doesnt do it in a multi line way. For example this is MY textbox:

[Date/Hour] You have entered the matrix
[Date/Hour] Thanks for entering the matrix.

and this is how it logs to the .TXT:

[Date/Hour] You have entered the matrix [Date/Hour] Thanks for entering the matrix.

This is the way i use it :

Private Sub CloseToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SalirToolStripMenuItem.Click
RichTextBox1.Text = RichTextBox1.Text & vbNewLine
Dim FILE_NAME As String = "C:log.txt"

[code].....

How can i make my .txt log to be as my textbox, multiline.