How to use textbox in DataGrid Colom to Select Me My Product

With very limited knowledge on what your application does and where you get your data from, it makes it extremely difficult to help or guide you.

Where do you store your information ? Do you hardcode it into your application or do you get it from an external source like a database, .DAT file, XML file, etc.
Do you understand what needs to be done to a DataGridView to update the information ?

Best advice I can give you at this time is to consider using a database backend to store all your information. You can then read the data from your databased and store it in a DataTable on the local machine. The DataTable is an indexed container holding whatever data you have selected from the database.

Once you have read the data into the DataTable you can now populate the AutoCompleteCustomSolution property of the textbox, set the AutoCompleteMode property of the same textbox to whatever you want it to do, eg: Suggest, Append, SuggestAppend, etc., then the last property you need to set is AutoCompleteSource - using the Custom Source setting will give you what you want.