Question

I have a CheckBox and a CheckBox list on my web page.
If the CheckBox is selected, all the CheckBoxes in the CheckBoxList should get selected, and if the CheckBox is unchecked, similarly all the CheckBoxes in the CheckBox should get deselected (unchecked).

.aspx code

<asp:CheckBoxList ID="CheckBoxList1" runat="server" 
            RepeatDirection="Horizontal" RepeatLayout="Flow">
            <asp:ListItem>Item A</asp:ListItem>
            <asp:ListItem>Item B</asp:ListItem>
            <asp:ListItem>Item C</asp:ListItem>
            <asp:ListItem Selected="True">Item D</asp:ListItem>
            <asp:ListItem>Item E</asp:ListItem>
            <asp:ListItem>Item F</asp:ListItem>
            <asp:ListItem>Item G</asp:ListItem>
        </asp:CheckBoxList>
<asp:CheckBox ID="allChkBox" Text="Select all" runat="server" 
                oncheckedchanged="allChkBox_CheckedChanged" />

I tried by doing somehting like this, but it didb’t work:

bool prevSelection = false;
protected void allChkBox_CheckedChanged(object sender, EventArgs e)
    {
if (!prevSelection)
        {
            foreach (ListItem chkitem in CheckBoxList1.Items)
            {
                chkitem.Selected = true;
            }
        }
        else
        {
            foreach (ListItem chkitem in CheckBoxList1.Items)
            {
                chkitem.Selected = false;
            }
        }
        prevSelection = !prevSelection;
}

Answer 1

I prefer to use client script for something like this so your page doesnt have to do a postback

If that is a possibility try firing a javascript function on click to do the looping and selecting … something like

<script type="text/javascript">
checked=false;
function checkedAll (frm1) {
    var aa= document.getElementById('frm1');
     if (checked == false)
          {
           checked = true
          }
        else
          {
          checked = false
          }
    for (var i =0; i < aa.elements.length; i++) 
    {
           if(aa.elements[i].type == 'checkbox') { 
             aa.elements[i].checked = checked;
           }
    }
 }
</script>