How to add "Find" function to IList

Question

I am returning IList from Business layer. But in viewmodel I have to use Find function. One method is to convert IList to List.

But is there anyway to add "Find" method to IList

Nicodemus

Just create your own IFindableList : IList implementation that includes the Find functionality. Since you control your own BL code you can return this FindableList – Troxler

Answer 1

Well, there are the Linq extension methods .Where (to fecth all that match) and .FirstOrDefault (to fetch the first match) or you can write your own extension method against IList like:

public static class IListExtensions
{
    public static T FindFirst<T>(this IList<T> source, Func<T, bool> condition)
    {
        foreach(T item in source)
            if(condition(item))
                return item;
        return default(T);
    }
}

Hacking

If I add this file to my .cs project, Can I access IListVar.FindFirst() ? – Nicodemus

Yes, as long as IListExtensions is in scope you will be able to call a FindFirst method against any IList<T>. – Hacking

What is ToList() method in Linq ?..Can I use this – Nicodemus

ToList will turn an IEnumerable<T> into a List<T>. – Hacking

Answer 2

you can use Where method

list.Where(predicate).First()

Occupation

list.First(predicate) will perform better than list.Where(predicate).First() as the second will enumerate all the list looking for more than one occurrence – Blaney

First() will raise an exception if item is not found, you want FirstOrDefault() to be the same behaviour as Find() – Bassett

Answer 3

Can you use the IndexOf method?

http://msdn.microsoft.com/en-us/library/3w0148af.aspx

Nicotinism

If you're using .net 3.5 or 5 you can use the .Select and get all elements in the IList that satisfy a condition msdn.microsoft.com/en-us/library/bb548891.aspx – Nicotinism

Is there anyway to Add these functions to IList – Nicodemus

I think that because an IList is IEnumerable that it already has these extension methods, have a look at msdn.microsoft.com/en-us/library/5y536ey6.aspx . – Nicotinism

Although, this is an IList<T>, you might have to cast to your specific type. – Nicotinism

Answer 4

very simple, just you need

casting step

var myModelasList= IListReturnedViewModel as List<ViewModelObject>;
//now you can use list feaures like Find Func.
myModelasList.Find((t => t.SomeFiald== currentState && t.IsSomting == somesymbol);

Blanc

Answer 5

I wrote an extension method to do the casting for me.

public static T Find<T>(this IList<T> ilist, Predicate<T> match)
{
  if (ilist is List<T> list)
  {
    return list.Find(match);
  }
  else if (ilist is T[] array)
  {
    return Array.Find(array, match);
  }
  else
  {
    return ilist.FirstOrDefault(i => match(i));
  }
}

Bassett