Put this as a property in your code behind:
public partial class WhateverYourClassNameIs
{
public String[] Selections
{
get
{
string[] sl = s.Split("$");
foreach (string s in sl)
{
ListItem itm = CheckBoxList1.Items.FindByValue(s);
if (itm != null) itm.Selected = true;
}
}
set
{
string s = string.Empty;
foreach (ListItem itm in CheckBoxList1.Items)
{
if (itm.Selected)
{
s += itm.Value + "$";
}
}
}
}
}