Question

I have an arraylist arrTotalItems of class Operation.Operation.

the class has two properties one is ID and name.
Now I have other arraylist arrSelectedItems which contain ID of operations

Now I have to bind two DataList to name of operation.

First DataList will be bind to selected arraylist.

Other DataList will be bind to arrTotalItems - arrSelectedItems that is those operations that are not in arrSelectedItems.

not able to find the logic how to bind both the lists

Answer 1

If you’re using version 3.5 or higher of the .NET Framework, LINQ allows you to project operations from the ids stored in arrSelectedItems with Select(), then use Except() to compute the intersection between arrTotalItems and this projection:

IEnumerable<Operation> totalOps = arrTotalItems.Cast<Operation>();
yourDataList.DataSource = totalOps.Except(arrSelectedItems.Cast<string>().Select(
    id => totalOps.Where(op => op.ID == id).FirstOrDefault()));

Note you first have to apply Cast<T>() to your ArrayLists in order to obtain instances of IEnumerable<T> that can be used with LINQ methods.