Checkbox in Gridview always returns false, ASP.NET, WEBFORM

I am developing a WebForm with Gridview to show a data that client will retrieve. But I have a problem with updating data in Gridview, after client checks the CheckBox hi will press a button to update the value in the database. But my checkbox always returns FALSE. I use .Net framework 4

public void Button_Submit_Onclick(object sender, EventArgs e)
    {

        for (int i = 0; i < GridView2.Rows.Count; i++)
        {
            con.ConnectionString = ConfigurationManager.ConnectionStrings["TestDeductionsConnectionString2"].ToString();
            int recordid = Convert.ToInt32(GridView2.DataKeys[i].Values[0]);
            bool private1 = Convert.ToBoolean(GridView2.FindControl("CheckBox1"));

            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "Update DetailCosts set  private='" + private1 + "' where recordid=" + recordid;
            con.Open();
            if (private1 == true)
            {

                cmd.Parameters.AddWithValue("@private1", SqlDbType.Bit).Value = private1;
                cmd.Parameters.AddWithValue("@recordid", SqlDbType.Int).Value = recordid.ToString();
            }
            else
            {
                cmd.Parameters.AddWithValue("@recordid", SqlDbType.Int).Value = recordid.ToString();
                cmd.Parameters.Add("@private1", SqlDbType.Bit).Value = private1;
            }
            cmd.ExecuteNonQuery();
            con.Close();
        }}

Here is a code for Gridview.

<asp:GridView ID="GridView2" runat="server"  AutoGenerateColumns="False" DataSourceID="SqlDataSource2" BackColor="White" BorderColor="#999999" BorderStyle="Solid" BorderWidth="1px" CellPadding="3" ForeColor="Black" GridLines="Vertical" DataKeyNames="recordid">
                            <AlternatingRowStyle BackColor="#CCCCCC" />
                            <Columns>
                                 <asp:BoundField DataField="recordid" HeaderText="recordid" SortExpression="recordid">
                                </asp:BoundField>
                                <asp:BoundField DataField="Employee" HeaderText="Employee" SortExpression="Employee">
                                </asp:BoundField>
                                <asp:BoundField DataField="mesec" HeaderText="Month" SortExpression="mesec">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="godina" HeaderText="Year" SortExpression="godina">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="CallDate" HeaderText="Call Date" SortExpression="CallDate">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="PhoneType" HeaderText="Phone Type" SortExpression="PhoneType">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="land" HeaderText="Land" SortExpression="land">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="number" HeaderText="Number" SortExpression="number">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="Minutes" HeaderText="Minutes" SortExpression="Minutes">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="Costs" HeaderText="Costs" SortExpression="Costs">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:BoundField DataField="privateCost" HeaderText="Private Costs" SortExpression="privateCost">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                                <asp:TemplateField HeaderText="Private" SortExpression="private" >
                                    <ItemTemplate>
                                        <asp:CheckBox  ID="CheckBox1" runat="server" Checked='<%# Eval("private") %>' />
                                    </ItemTemplate>
                                    <HeaderStyle HorizontalAlign="Center" />
                                </asp:TemplateField>
                                <asp:BoundField DataField="Komentar" HeaderText="Commnet" SortExpression="Komentar">
                                    <ItemStyle HorizontalAlign="Center" />
                                </asp:BoundField>
                            </Columns>
                            <FooterStyle BackColor="#CCCCCC" />
                            <HeaderStyle BackColor="Black" Font-Bold="True" ForeColor="White" />
                            <PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
                            <SelectedRowStyle BackColor="#000099" Font-Bold="True" ForeColor="White" />
                            <SortedAscendingCellStyle BackColor="#F1F1F1" />
                            <SortedAscendingHeaderStyle BackColor="#808080" />
                            <SortedDescendingCellStyle BackColor="#CAC9C9" />
                            <SortedDescendingHeaderStyle BackColor="#383838" />
                        </asp:GridView>