Question

I have this code (which is way simplified from the real code):

public interface IAmount
{
  decimal Amount { get; set; }
}

public class SomeAmount : IAmount
{
  public decimal Amount { get; set; }
}

public static void UpdateAmounts( this IEnumerable< IAmount > amounts, decimal totalAmount )
{
  foreach ( IAmount amount in amounts )
    amount.Amount = GetAmount();      
}

public static decimal GetAmount()
{
  return 12345m;
}

The code works great and the UpdateAmounts ExtensionMethod is used quite frequently throughout the application to apply a penny rounding routine (not like the one in Office Space!)

The problem is I do not like having an IAmount interface with a specific name of the column I need to set (Amount). In a new requirement, I need to update a database entity collection with this routine and the name of the property I need to update is “GrossAmount”. Sometimes too it would be nice to update other writable decimal properties in a similar manner.

The problem is that it appears I cannot simple say amount.Field = GetAmount() where the .Field part deals with a different property on the entity. Is it possible somehow? I am not on C# 4.0, so using a dynamic type isn’t possible for me yet.

Answer 1

You could do this in a more functional style, something like this:

    public class Something
    {
        public decimal Amount { get; set; }
        public decimal OtherAmount { get; set; }
    }

    public static void UpdateAmounts<T, U>(IEnumerable<T> items, Action<T,U> setter, Func<T, U> getter)
    {
        foreach (var o in items)
        {
            setter(o, getter(o));
        }
    }

    public void QuickTest()
    {
        var s = new [] { new Something() { Amount = 1, OtherAmount = 11 }, new Something() { Amount = 2, OtherAmount = 22 }};
        UpdateAmounts(s, (o,v) => o.Amount = v, (o) => o.Amount + 1);
        UpdateAmounts(s, (o,v) => o.OtherAmount = v, (o) => o.OtherAmount + 2);
    }