<GridViewColumn Width="30">
    <GridViewColumn.CellTemplate>
        <DataTemplate>
            <Button Width="15" Margin="2, 0, 0, 0">
            +
            </Button>
        </DataTemplate>
    </GridViewColumn.CellTemplate>
</GridViewColumn>

public class Product
{
    public string Title { get; set; }
    public int Number { get; set; }
    public int Price { get; set; }
    public string Placement { get; set; }
    public int NumPrice { get; set; }
}

List<Product> products;

products.Add(new Product { Title = "Adobe Photoshop", Number = 1, NumPrice = 10, Price = 20, Placement = "в наличии (скидка 50%)" });
LW.Items.Refresh();