Question

At my form, I have one control ComboBox. I want after databinding add text “Select”. I try this

cbOperatorList.DataSource = operatorService.GetOperatorList();
cbOperatorList.Items.Insert(0, "Select");

But when I do this. I get exception what

Changing the collection of items is impossible if you set the property
DataSource.

UPDATE

public BindingList<Operator> GetOperatorList(string filter = "")
{
            return
                new BindingList<Operator>(
                    this.operatorRepository.All.Where(
                        item => item.FirtsName.Contains(filter) || item.LastName.Contains(filter) || item.MiddleName.Contains(filter)).
                        ToList());
}

UPDATE

I fixed the problem, using this code

cbOperatorList.DataSource =
                this.operatorService.GetOperatorList().Concat(new[] { new Operator { LastName = "Select", Id = 0 } }).OrderBy(
                    item => item.Id).ToList();

Answer 1

If GetOperatorList() returns an immutable IEnumerable<T>, you can use linq to concatenate that with new object[] { "Select" }. Assuming that T is not object, you would have to cast:

cbOperatorList.DataSource = operatorService
    .GetOperatorList()
    .Cast<object>()
    .Concat(new object[] { "Select" }); 

EDIT

If you want the word “Select” to appear at the beginning, reverse the concatenation:

cbOperatorList.DataSource = (new object[] { "Select" })
    .Concat(
        operatorService.GetOperatorList().Cast<object>()
     );