Question

I have an IList<T> that I need to sort, and I would rather not copy the list if possible. I’ve noticed that ArrayList has an Adapter static method that wraps the passed list without copying it, but this takes an IList and I have an IList<T>. Is it safe to cast from a System.Collections.Generic.IList<T> to a System.Collections.IList and just use the Adapter method?

Note that this is .Net 2.0, so LINQ is not an option.

Answer 1

From the blog of Paul Fox, I recommend the post ‘How to sort an IList’: http://foxsys.blogspot.com/2007/06/how-to-sort-generic-ilist.html

Just in case that blog goes away in the future, I’ll copy the post here:

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How to sort a generic IList

Update

You can read and updated post about sorting generic IList and List. Many people will prefer the methods mentioned in the updated post.

Sorting a generic IList

I was trying to sort a generic IList<> and found a fairly simple way of doing it.

Step 1

You need to implement IComparable for the type contained in your IList. For this example I am going to use a simple Language Dto class.

public class LanguageDto : IComparable {  private String name;  public string Name { get { return name; } set { name = value; } }   public LanguageDto(string name) {      this.name = name;  }   #region IComparable Members  public int CompareTo(object obj) {      if (obj is LanguageDto) {      LanguageDto language = (LanguageDto)obj;      return this.name.CompareTo(language.name);      }      throw new ArgumentException(string.Format('Cannot compare a LanguageDto to an {0}', obj.GetType().ToString()));  }  #endregion } 

STEP 2

Sort your IList. To do this you will use the ArrayList.Adapter() method passing in your IList, and then calling the Sort method. Like so…

ArrayList.Adapter((IList)languages).Sort(); 

Note: languages is of type ‘IList’

Languages should then be a sorted list of your type!