Hello
Try to make your logic as folloiwng way
Concate ID and IsModified , assign to Value field
for (int i = 0; i < dt1.Rows.Count; i++)
{
string strName = dt1.Rows[i]["Name"].ToString();
string strID = dt1.Rows[i]["ID"].ToString() + "|" + dt1.Rows[i]["IsModified"].ToString();
ListItem li = new ListItem(strName, strID);
if (!lbSelected.Items.Contains(li))
{
lbAvailable.Items.Add(li);
}
}
Now on page Prerender event , Split this Value and assign attribute
protected void Page_PreRender(object sender, EventArgs e)
{
for (int j = 0; j < lbAvailable.Items.Count; j++)
{
string AppliedValue = lbAvailable.Items[j].Value.Split('|')[1].ToString();
lbAvailable.Items[j].Attributes.Add("C", AppliedValue);
}
for (int j = 0; j < lbSelected.Items.Count; j++)
{
string AppliedValue = lbSelected.Items[j].Value.Split('|')[1].ToString();
lbSelected.Items[j].Attributes.Add("C", AppliedValue);
}
}