Add more columns to GridView - asp.net

Question

I have a GridView, which is bound to a database table. This GridView shows the some books (price, author information, etc).
I wants to add a column "Add to Cart" to this GridView at the end of each book. I added one column with text "Add to cart". But, on debug, it shows an error as "Add to cart is not present in db."
So please tell me how to append this column to the GridView.
Markup
<asp:GridView ID="GridView1" runat="server" BorderStyle="Double"
BorderWidth="3px" CellPadding="4" GridLines="Horizontal" Height="260px"
Width="661px">
<FooterStyle BackColor="White" ForeColor="#333333" />
<HeaderStyle BackColor="#336666" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#336666" ForeColor="White" HorizontalAlign="Center" />
<RowStyle BackColor="White" ForeColor="#333333" />
<SelectedRowStyle BackColor="#339966" Font-Bold="True" ForeColor="White" />
<SortedAscendingCellStyle BackColor="#F7F7F7" />
<SortedAscendingHeaderStyle BackColor="#487575" />
<SortedDescendingCellStyle BackColor="#E5E5E5" />
<SortedDescendingHeaderStyle BackColor="#275353" />
<Columns>
<asp:ButtonField Text="Add To Cart">
<FooterStyle HorizontalAlign="Right" />
<HeaderStyle HorizontalAlign="Right" />
<ItemStyle HorizontalAlign="Left" />
</asp:ButtonField>
</Columns>
</asp:GridView>
Code
public partial class WebForm9 : System.Web.UI.Page<p>
{
buybl obj = new buybl();
protected void Page_Load(object sender, EventArgs e)
{
obj.dept = "IT";
GridView1.DataSource = obj.select();
GridView1.DataBind();
}
}

Answer 1

Without your markup, it's hard to say. But, it sounds like you may have modelled the "Add To Cart" column after your columns that are bound to the database. You probably have your databound columns set up as BoundFields like this:
<Columns>
<asp:BoundField DataField="Title" HeaderText="Book Title" />
<asp:BoundField DataField="Author" HeaderText="Book Author" />
<asp:BoundField DataField="Price" HeaderText="Book Price" />
</Columns>
Your "Add To Cart" column will not be databound. If you just want to add a column that has a static button, you can add a CommandField to your GridView, like this:
<Columns>
<asp:BoundField DataField="Title" HeaderText="Book Title" />
<asp:BoundField DataField="Author" HeaderText="Book Author" />
<asp:BoundField DataField="Price" HeaderText="Book Price" />
<asp:CommandField SelectText="Add To Cart" ShowSelectButton="True" />
</Columns>
Or you can just add AutoGenerateSelectButton="True" to your GridView markup. Then you can handle the adding of items to your cart in the RowCommand or SelectedIndexChanged events that are fired when you click the Select button

Answer 2

you can add column like this in gridview
<asp:TemplateField >
<HeaderTemplate >
<asp:Button ID="ButtonName" runat="server" Text="Add to Cart" > </asp:Button>
</HeaderTemplate>
</asp:TemplateField>

Answer 3

Use the TemplateField column type -- unlimited customization:
http://msdn.microsoft.com/en-us/library/bb288032.aspx
<asp:TemplateField HeaderText="FirstName" SortExpression="FirstName">
<EditItemTemplate>
<asp:TextBox ID="TextBox1" runat="server" Text='<% #Bind("FirstName") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<% #Bind("FirstName") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>