How can I set checkboxlist items as checked by default - asp.net

Question

In my page i have a CheckBoxList control and i would like all the checkboxes to be checked by default. how can i do that? i have tried couple ways but it is not doing it. here is my code behind:
protected void chkAll_CheckedChanged(object sender, EventArgs e)
{
foreach(GridViewRow gr in GridView1.Rows)
{
CheckBox cb = (CheckBox)gr.FindControl("chkItem");
cb.Checked = true;
if(((CheckBox)sender).Checked)
cb.Checked = true;
else
cb.Checked = false;
}
}
and here is my ASPX code:
<asp:TemplateField HeaderText="Check All">
<HeaderTemplate>
<asp:CheckBox ID="chkAll" runat="server" AutoPostBack="True" OnCheckedChanged="chkAll_CheckedChanged" />
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID="chkItem" runat="server" />
</ItemTemplate>
</asp:TemplateField>

Answer 1

Use the following ASPX:
<asp:GridView runat="server" ID="m_gridView" AutoGenerateColumns="False">
<Columns>
<asp:TemplateField HeaderText="Check All">
<HeaderTemplate>
<asp:CheckBox ID="chkAll" runat="server" AutoPostBack="True" OnCheckedChanged="chkAll_CheckedChanged" Checked="True" />
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID="chkItem" runat="server" Checked="True" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
It should have Check All and the individual check boxes checked by default.
In you code behind do the following:
protected void chkAll_CheckedChanged(object sender, EventArgs e)
{
CheckBox l_cbAll = (CheckBox)m_gridView.HeaderRow.FindControl("chkAll");
foreach (GridViewRow l_row in m_gridView.Rows)
{
CheckBox l_cb = (CheckBox)l_row.FindControl("chkItem");
l_cb.Checked = l_cbAll.Checked;
}
}