C# geting values from database to datagridview

I have a Combobox and  add button combobox will be populate on form load and contains Item_No as ValueMember and Item_Name as Display Member

 

Now when user select a item in combobox and clicks on add button i want to add Item_No,Item_Name and Item Price in datagridview every button click these values will be inserted at last in datagridview. can anybody tell me the solution for that