{ Code: Impossible }

What is wrong with the code below? Safe Assumptions:

1. _dictionary is a valid non-null Dictionary<object,object>
2. _dictionary contains items that will match the passed expression
3. This code compiles with no warnings or errors
4. This code will throw an exception at runtime.

public IList<TModel> GetAllByCriteria<TModel> ( Expression<Func<TModel, bool>> criteria )
{
    Func<TModel, bool> action = criteria.Compile();
    return _dictionary.Where( pair => 
        action( (TModel)pair.Value ) ).Cast<TModel>().ToList();
}

If you don’t see it right away then you’re not alone. I spent a while debugging to catch this. If you do see it right away then pat yourself on the back.