Question

I have a fairly complex scenario and I need to ensure items I have in a list are sorted.

Firstly the items in the list are based on a struct that contains a sub struct.

For example:

public struct topLevelItem
{
 public custStruct subLevelItem;
}

public struct custStruct
{
  public string DeliveryTime;
}

Now I have a list comprised of topLevelItems for example:

var items = new List<topLevelItem>();

I need a way to sort on the DeliveryTime ASC. What also adds to the complexity is that the DeliveryTime field is a string. Since these structs are part of a reusable API, I can’t modify that field to a DateTime, neither can I implement IComparable in the topLevelItem class.

Any ideas how this can be done?

Thank you

Answer 1

It sounds like you need to get canonicalized date sorting even though your date is represented as a string, yes? Well, you can use LINQ’s OrderBy operator, but you will have to parse the string into a date to achieve correct results:

items = items.OrderBy(item => DateTime.Parse(item.subLevelItem.DeliveryTime))
             .ToList(); 

Update:

I’ve added this in for completeness – a real example of how I use ParseExact with Invariant culture:

var returnMessagesSorted = returnMessages.OrderBy((item => DateTime.ParseExact(item.EnvelopeInfo.DeliveryTime, ISDSFunctions.GetSolutionDateTimeFormat(), CultureInfo.InvariantCulture)));
return returnMessagesSorted.ToList();

You can always implement a separate IComparer class, it’s not fun, but it works well:

public class TopLevelItemComparer : IComparer<topLevelItem>
{
  public int Compare( topLevelItem x, topLevelItem y )
  {
      return DateTime.Parse(x.subLevelItem.DeliveryTime).CompareTo(
             DateTime.Parse(y.subLevelItem.DeliveryTime) );
  }
}

items.Sort( new TopLevelItemComparer() );

Be aware that most Sort() methods in the .NET framework accept an IComparer or IComparer<T> which allows you to redefine the comparison semantics for any type. Normally, you just use Comparer<T>.Default – or use an overload that essentially supplies this for you.