Question

I have a number of objects defined, each has a property named “CreateDate”.

Is it possible to write a single, generic method to select the highest date from an object that I specify?

I was attempting to use a generic approach to this, but the compiler doesn’t like it when I try to specify a property name.

I was trying to achieve something along these lines…

private static DateTime GetLastDate<T>(List<T> data)
{
    // Unfortunately, this is not allowed...
    return
        (from d in data
        orderby d.CreateDate
        select d.CreateDate).FirstOrDefault();
}

Answer 1

The best method would be to create an interface with the specific functionality and have all of the classes implement that interface:

public interface ICreated
{
  public DateTime CreateDate {get;}
}

Then you can ensure that all of the items accepted implement that interface:

private static DateTime GetLastDate<T>(IEnumerable<T> input) where T : ICreated
{
    return input.Max(d=>d.CreateDate);
}

If that’s really not an option (possibly because you can’t modify the class to have it implement the interface or the collection to wrap the underlying type) you could use dynamic. I would highly discourage that you do this as it’s really not good design, it will be much slower, and it’s rather susceptible to breaking, but it could work:

private static DateTime GetLastDate(IEnumerable<dynamic> input)
{
    return input.Max(d=>d.CreateDate);
}