Question

I am looking for a linq to entities query which does the equivalent of the following SQL.

select null, '<None>'
union select CustomerId, Customer from Customers

I would then bind the resulting list of objects (which could be instances of an explicit class or an anonymous class) as the list source for a combo box. I don’t need all the fields of the Customer entity class but if the resulting list of objects were instances of this class rather than a ‘stub’ class that wouldn’t be a big problem, but obviously there would be some memory wastage.

Answer 1

Do it in memory:

Ext.ToEnumerable(new {CustomerId = 0, Name = "<none>"})
    .Concat(db.Customers
        .Select(c => new {CustomerId = c.CustomerId, Name = c.Name}).ToList());

Where ToEnumerable is a nice little utility function:

public static class Ext
{
    public static IEnumerable<T> ToEnumerable<T>(params T[] items)
    {
        return items;
    }
}

Note that I use CustomerId = 0 (not null) to make sure the anonymous type match. It is even better to use a named type with the two fields (CustomerId and Name).