Question

I’m trying to create a public property, which could either be of type long or Guid. Is it possible with generics? e.g. something like

public virtual T where T: long or Gui Id { get; set; }

Answer 1

Is it possible with generics?

It is not possible, but you can work around by using use implicit operator to support both long and Guid, sample code:

internal class YourId
{
    public long LongId { get; private set; }
     public Guid GuidId { get; private set; }

    public YourId(long longValue)
    {
        LongId = longValue;
    }

    public YourId(Guid guidValue)
    {
        GuidId = guidValue;
    }

    public static implicit operator long(YourId yourId)
    {
        return yourId.LongId;
    }

    public static  implicit operator YourId(long value)
    {
        return new YourId(value);
    }

       public static implicit operator Guid(YourId yourId)
    {
        return yourId.GuidId;
    }

    public static  implicit operator YourId(Guid value)
    {
        return new YourId(value);
    }
}

Now you can use:

YourId id1 = Guid.NewGuid();
YourId id2 = long.MaxValue;