Help me C#!

Question

Hi ! everyone ! I'm student
I have a problem about my project
My project :

i need enter a new Row on datatable and database will upraise to Datagridview on Form

I use code to add new row : 
  DataRow n = tb.NewRow();
 n["FoodName"] = "Pepsi";
 n["Quantity"] = 1;
 tb.Rows.Add(n);


datagridview:

i have a datagridview
  FoodName (Column)| Quantity(Column)

FoodName	Quantity

i want while I click button [Pepsi] , My datagrid will :

FoodName	Quantity
Pepsi	1

 If I Second Click button[pepsi] , my datagird will:....and ect.........Thirth......Fourth...... quantity will 3,4.....

FoodName	Quantity
Pepsi	2

as button CocaCola , Button Coffee
 

Please Help me !!
my e-mail: [email protected] 
you can send e-mail for me !! Thankyou Everyone read !!!