Gridview data bond twice

I defined -
<asp:GridView ID="GridView1" runat="server" BackColor="#FFFFFF"
                    ForeColor="#5078B3" AlternatingRowStyle-BackColor="#F0F0F0" >

In C#, I have the following and the gridview is filled with data.
            rdr = cmd.ExecuteReader();
            GridView1.DataSource = rdr;
            GridView1.DataBind();

Now I want add Select command button on the first column of each row. I added as following -

<asp:GridView ID="GridView1" runat="server" BackColor="#FFFFFF"
                    ForeColor="#5078B3" AlternatingRowStyle-BackColor="#F0F0F0"
                    OnDataBound="GridView1_DataBound">
           <Columns>                    
                    <asp:CommandField HeaderText="Select" ShowSelectButton="True"/>
                    <asp:BoundField DataField="itemId" HeaderText="Item ID"/>
                    <asp:BoundField DataField="Equipment" HeaderText="Equipment" />
                    <asp:BoundField DataField = .......
                    .....
               </Columns>
               <headerstyle .....
In C#, I added -
protected void GridView1_DataBound(object sender, EventArgs e)
    {
        GridView1.HeaderRow.Cells[0].Width = new Unit(80, UnitType.Pixel);
        GridView1.HeaderRow.Cells[1].Width = new Unit(80, UnitType.Pixel);
        GridView1.HeaderRow.Cells[2].Width = new Unit(100, UnitType.Pixel);
        GridView1.HeaderRow.Cells[3].Width = new Unit(100, UnitType.Pixel);
        ....        
        ....
        foreach (TableRow row in GridView1.Rows)
        {
            row.Cells[0].Width = new Unit(80, UnitType.Pixel);
            row.Cells[1].Width = new Unit(80, UnitType.Pixel);
            row.Cells[2].Width = new Unit(100, UnitType.Pixel);
            row.Cells[3].Width = new Unit(100, UnitType.Pixel);
            ...            
            ...            
        }
    }

Now I got two sets of data - one set with Select button and one without.
How can I get rid of the one set that does not have the Select command button? I still need to set   rdr = cmd.ExecuteReader(); GridView1.DataSource = rdr; GridView1.DataBind(); right?

Thanks.