CheckListBox Select-Clear All Button example. Because I feel like it.
<asp:Button ID="btnSelect" Runat="server" OnCommand="btnSelect_OnCommand" />
protected void btnSelect_OnCommand(object sender, CommandEventArgs e)
{
string action = e.CommandArgument.ToString();
bool blnSelected;
if (action == "selectall")
{
btnSelect.CommandArgument = "clear";
btnSelect.Text = "Clear All";
blnSelected = true;
}
else
{
btnSelect.CommandArgument = "selectall";
btnSelect.Text = "Select All";
blnSelected = false;
}
foreach(ListItem cb in chklstMembers.Items)
{
cb.Selected = blnSelected;
}
}