Recently I am working on windows based application after a long back in which I am using ChekedListBox control where I need to list all the subdistricts information based on the selected district in other dropdownList Control.

In this way, I want to have a Select ALL item as the first checkbox in the CheckedListBox. When I click on ‘ALL’ remaining all checkbox should be checked and vise versa.

Following is code snippet to implement this functionality in SelectedIndexChanged event occurs

bool isSelectAll = false;

if (chkSubDistrict.CheckedItems.Contains("All"))
{
    isSelectAll = true;
}
else
{
    isSelectAll = false;
}

for (int i = 0; i < chkSubDistrict.Items.Count; i++)
{
    if (chkSubDistrict.Items[i].ToString() != "All")
       chkSubDistrict.SetItemChecked(i, isSelectAll);
}

Here the above code is self-explanatory. Just a small snippet hope it makes you some help.