using Textbox to update DataGrid, while working with Databases

Question

how can the textbox contents to be transferred identically to the DataGrid in the column?
My WPF textbox is Multiline, and users type its contents in the textbox continuously, and its contents would go to the next line after reaching end of the line in the textbox.

However, when it is saved to the Database, those contents from the textbox would just appear as a SINGLE LONG line in the DataGrid.

Any constructive comments are highly appreciated.