ASP.NET

<form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="userid"
            DataSourceID="SqlDataSource1" Height="137px" Width="195px">
            <Columns>
                <asp:BoundField DataField="userid"  HeaderText="userid" ReadOnly="True" SortExpression="userid" />
                <asp:BoundField DataField="username" HeaderText="username" SortExpression="username" />
                <asp:BoundField DataField="city" HeaderText="city" SortExpression="city" />
                <asp:TemplateField HeaderText="select">
                <ItemTemplate>
                <asp:CheckBox ID="chkbx" runat="server" /></ItemTemplate></asp:TemplateField>
            </Columns>
        </asp:GridView>
    
    </div>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
            SelectCommand="SELECT * FROM [user]"></asp:SqlDataSource>
        <br />
        <br />
        <asp:Button ID="Button1" runat="server" Height="28px" OnClick="Button1_Click" Text="Transfer"
            Width="82px" />
        <br />
        <br />
        <br />
        <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False" >
        </asp:GridView>
    </form>

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        {
            DataTable dt = new DataTable();
            DataRow dr;

            dt.Columns.Add(new DataColumn("userid"));
            dt.Columns.Add(new DataColumn("username"));
            dt.Columns.Add(new DataColumn("city"));

            foreach (GridViewRow gr in GridView1.Rows)
            {
                //if (((CheckBox)(gr.FindControl("chkbx"))).Checked == true)

                if (((CheckBox)gr.Cells[3].FindControl("chkbx")).Checked == true)
                {
                    dr = dt.NewRow();
                    dr["userid"] = gr.Cells[0].Text;
                    dr["username"] = gr.Cells[1].Text;
                    dr["city"] = gr.Cells[2].Text;
                    dt.Rows.Add(dr);
                }
            }
            GridView2.DataSource = dt;
            GridView2.DataBind();
        }
    }
}