Sorting an IList in C

Question

So I came across an interesting problem today  We have a WCF web service that returns an IList  Not really a big deal until I wanted to sort it   Turns out the IList interface doesn t have a sort method built in    I ended up using the ArrayList Adapter list  Sort new MyComparer    method to solve the problem but it just seemed a bit  ghetto  to me   I toyed with writing an extension method  also with inheriting from IList and implementing my own Sort   method as well as casting to a List but none of these seemed overly elegant   So my question is  does anyone have an elegant solution to sorting an IList

User · Answer

Useful for grid sorting this method sorts list based on property names  As follow the example       List lt MeuTeste gt  temp   new List lt MeuTeste gt          temp Add new MeuTeste 2   ramster   DateTime Now        temp Add new MeuTeste 1   ball   DateTime Now        temp Add new MeuTeste 8   gimm   DateTime Now        temp Add new MeuTeste 3   dies   DateTime Now        temp Add new MeuTeste 9   random   DateTime Now        temp Add new MeuTeste 5   call   DateTime Now        temp Add new MeuTeste 6   simple   DateTime Now        temp Add new MeuTeste 7   silver   DateTime Now        temp Add new MeuTeste 4   inn   DateTime Now         SortList ref temp  SortDirection Ascending   MyProperty         private void SortList lt T gt       ref List lt T gt  lista       SortDirection sort       string propertyToOrder                if   string IsNullOrEmpty propertyToOrder           amp  amp  lista    null          amp  amp  lista Count  gt  0                        Type t   lista 0  GetType                 if  sort    SortDirection Ascending                                lista   lista OrderBy                      a   gt  t InvokeMember                          propertyToOrder                           System Reflection BindingFlags GetProperty                           null                           a                           null                                         ToList                              else                               lista   lista OrderByDescending                      a   gt  t InvokeMember                          propertyToOrder                           System Reflection BindingFlags GetProperty                           null                           a                           null                                         ToList

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Found this thread while I was looking for a solution to the exact problem described in the original post  None of the answers met my situation entirely  however  Brody s answer was pretty close  Here is my situation and solution I found to it   I have two ILists of the same type returned by NHibernate and have emerged the two IList into one  hence the need for sorting   Like Brody said I implemented an ICompare on the object  ReportFormat  which is the type of my IList    public class FormatCcdeSorter IComparer lt ReportFormat gt               public int Compare ReportFormat x  ReportFormat y                       return x FormatCode CompareTo y FormatCode                     I then convert the merged IList to an array of the same type   ReportFormat   myReports   new ReportFormat reports Count     reports is the merged IList   Then sort the array    Array Sort myReports  new FormatCodeSorter      sorting using custom comparer   Since one-dimensional array implements the interface System Collections Generic IList lt T gt   the array can be used just like the original IList

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In VS2008  when I click on the service reference and select  Configure Service Reference   there is an option to choose how the client de-serializes lists returned from the service   Notably  I can choose between System Array  System Collections ArrayList and System Collections Generic List

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try this    USE ORDER BY         public class Employee               public string Id   get  set            public string Name   get  set            private static IList lt Employee gt  GetItems                         List lt Employee gt  lst   new List lt Employee gt                  lst Add new Employee   Id    1   Name    Emp1                  lst Add new Employee   Id    2   Name    Emp2                  lst Add new Employee   Id    7   Name    Emp7                  lst Add new Employee   Id    4   Name    Emp4                  lst Add new Employee   Id    5   Name    Emp5                  lst Add new Employee   Id    6   Name    Emp6                  lst Add new Employee   Id    3   Name    Emp3                   return lst               var lst   GetItems   AsEnumerable                 var orderedLst   lst OrderBy t   gt  t Id  ToList                 orderedLst ForEach emp   gt  Console WriteLine  Id -  0  Name - 1    emp Id  emp Name

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The accepted answer by  DavidMills is quite good  but I think it can be improved upon   For one  there is no need to define the ComparisonComparer lt T gt  class when the framework already includes a static method Comparer lt T gt  Create Comparison lt T gt     This method can be used to create an IComparison on the fly   Also  it casts IList lt T gt  to IList which has the potential to be dangerous   In most cases that I have seen  List lt T gt  which implements IList is used behind the scenes to implement IList lt T gt   but this is not guaranteed and can lead to brittle code   Lastly  the overloaded List lt T gt  Sort   method has 4 signatures and only 2 of them are implemented    List lt T gt  Sort   List lt T gt  Sort Comparison lt T gt   List lt T gt  Sort IComparer lt T gt   List lt T gt  Sort Int32  Int32  IComparer lt T gt     The below class implements all 4 List lt T gt  Sort   signatures for the IList lt T gt  interface   using System  using System Collections Generic   public static class IListExtensions       public static void Sort lt T gt  this IList lt T gt  list                if  list is List lt T gt                           List lt T gt  list  Sort                      else                       List lt T gt  copy   new List lt T gt  list               copy Sort                Copy copy  0  list  0  list Count                        public static void Sort lt T gt  this IList lt T gt  list  Comparison lt T gt  comparison                if  list is List lt T gt                           List lt T gt  list  Sort comparison                     else                       List lt T gt  copy   new List lt T gt  list               copy Sort comparison               Copy copy  0  list  0  list Count                        public static void Sort lt T gt  this IList lt T gt  list  IComparer lt T gt  comparer                if  list is List lt T gt                           List lt T gt  list  Sort comparer                     else                       List lt T gt  copy   new List lt T gt  list               copy Sort comparer               Copy copy  0  list  0  list Count                        public static void Sort lt T gt  this IList lt T gt  list  int index  int count          IComparer lt T gt  comparer                if  list is List lt T gt                           List lt T gt  list  Sort index  count  comparer                     else                       List lt T gt  range   new List lt T gt  count               for  int i   0  i  lt  count  i                                  range Add list index   i                              range Sort comparer               Copy range  0  list  index  count                        private static void Copy lt T gt  IList lt T gt  sourceList  int sourceIndex          IList lt T gt  destinationList  int destinationIndex  int count                for  int i   0  i  lt  count  i                          destinationList destinationIndex   i    sourceList sourceIndex   i                       Usage   class Foo       public int Bar       public Foo int bar    this Bar   bar       void TestSort         IList lt int gt  ints   new List lt int gt      1  4  5  3  2        IList lt Foo gt  foos   new List lt Foo gt                  new Foo 1           new Foo 4           new Foo 5           new Foo 3           new Foo 2               ints Sort        foos Sort  x  y    gt  Comparer lt int gt  Default Compare x Bar  y Bar        The idea here is to leverage the functionality of the underlying List lt T gt  to handle sorting whenever possible   Again  most IList lt T gt  implementations that I have seen use this   In the case when the underlying collection is a different type  fallback to creating a new instance of List lt T gt  with elements from the input list  use it to do the sorting  then copy the results back to the input list   This will work even if the input list does not implement the IList interface

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Here s an example using the stronger typing  Not sure if it s necessarily the best way though   static void Main string   args        IList list   new List lt int gt      1  3  2  5  4  6  9  8  7        List lt int gt  stronglyTypedList   new List lt int gt  Cast lt int gt  list        stronglyTypedList Sort       private static IEnumerable lt T gt  Cast lt T gt  IEnumerable list        foreach  T item in list                yield return item            The Cast function is just a reimplementation of the extension method that comes with 3 5 written as a normal static method  It is quite ugly and verbose unfortunately

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Is this a valid solution           IList lt string gt  ilist   new List lt string gt             ilist Add  B            ilist Add  A            ilist Add  C             Console WriteLine  IList            foreach  string val in ilist              Console WriteLine val           Console WriteLine             List lt string gt  list    List lt string gt  ilist          list Sort            Console WriteLine  List            foreach  string val in list              Console WriteLine val           Console WriteLine             list   null           Console WriteLine  IList again            foreach  string val in ilist              Console WriteLine val           Console WriteLine      The result was  IList B A C  List A B C  IList again A B C

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This looks MUCH MORE SIMPLE if you ask me  This works PERFECTLY for me   You could use Cast   to change it to IList then use OrderBy         var ordered   theIList Cast lt T gt    OrderBy e   gt  e     WHERE T is the type eg  Model Employee or Plugin ContactService Shared Contact  Then you can use a for loop and its DONE     ObservableCollection lt Plugin ContactService Shared Contact gt  ContactItems  new ObservableCollection lt Contact gt          foreach  var item in ordered               ContactItems Add item

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How about using LINQ To Objects to sort for you   Say you have a IList lt Car gt   and the car had an Engine property  I believe you could sort as follows   from c in list orderby c Engine select c    Edit  You do need to be quick to get answers in here  As I presented a slightly different syntax to the other answers  I will leave my answer - however  the other answers presented are equally valid

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using System Linq   var yourList   SomeDAO GetRandomThings    yourList ToList   Sort   thing  randomThing    gt  thing CompareThisProperty CompareTo  randomThing CompareThisProperty        That s pretty  ghetto

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Convert your IList into List lt T gt  or some other generic collection and then you can easily query sort it using System Linq namespace  it will supply bunch of extension methods

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This question inspired me to write a blog post  http   blog velir com index php 2011 02 17 ilistt-sorting-a-better-way   I think that  ideally  the  NET Framework would include a static sorting method that accepts an IList lt T gt   but the next best thing is to create your own extension method  It s not too hard to create a couple of methods that will allow you to sort an IList lt T gt  as you would a List lt T gt   As a bonus you can overload the LINQ OrderBy extension method using the same technique  so that whether you re using List Sort  IList Sort  or IEnumerable OrderBy  you can use the exact same syntax   public static class SortExtensions           Sorts an IList lt T gt  in place      public static void Sort lt T gt  this IList lt T gt  list  Comparison lt T gt  comparison                ArrayList Adapter  IList list  Sort new ComparisonComparer lt T gt  comparison                  Sorts in IList lt T gt  in place  when T is IComparable lt T gt      public static void Sort lt T gt  this IList lt T gt  list  where T  IComparable lt T gt                Comparison lt T gt  comparison    l  r    gt  l CompareTo r           Sort list  comparison                  Convenience method on IEnumerable lt T gt  to allow passing of a        Comparison lt T gt  delegate to the OrderBy method      public static IEnumerable lt T gt  OrderBy lt T gt  this IEnumerable lt T gt  list  Comparison lt T gt  comparison                return list OrderBy t   gt  t  new ComparisonComparer lt T gt  comparison                Wraps a generic Comparison lt T gt  delegate in an IComparer to make it easy    to use a lambda expression for methods that take an IComparer or IComparer lt T gt  public class ComparisonComparer lt T gt    IComparer lt T gt   IComparer       private readonly Comparison lt T gt   comparison       public ComparisonComparer Comparison lt T gt  comparison                 comparison   comparison             public int Compare T x  T y                return  comparison x  y              public int Compare object o1  object o2                return  comparison  T o1   T o2             With these extensions  sort your IList just like you would a List   IList lt string gt  iList   new           Carlton    Alison    Bob    Eric    David         Use the custom extensions      Sort in-place  by string length iList Sort  s1  s2    gt  s1 Length CompareTo s2 Length        Or use OrderBy   IEnumerable lt string gt  ordered   iList OrderBy  s1  s2    gt  s1 Length CompareTo s2 Length      There s more info in the post  http   blog velir com index php 2011 02 17 ilistt-sorting-a-better-way

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You can use LINQ   using System Linq   IList lt Foo gt  list   new List lt Foo gt     IEnumerable lt Foo gt  sortedEnum   list OrderBy f  gt f Bar   IList lt Foo gt  sortedList   sortedEnum ToList

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Found a good post on this and thought I d share  Check it out HERE  Basically   You can create the following class and IComparer Classes  public class Widget       public string Name   string Empty      public int Size   0       public Widget string name  int size        this Name   name      this Size   size       public class WidgetNameSorter   IComparer lt Widget gt        public int Compare Widget x  Widget y            return x Name CompareTo y Name        public class WidgetSizeSorter   IComparer lt Widget gt        public int Compare Widget x  Widget y        return x Size CompareTo y Size         Then If you have an IList  you can sort it like this   List lt Widget gt  widgets   new List lt Widget gt     widgets Add new Widget  Zeta   6    widgets Add new Widget  Beta   3    widgets Add new Widget  Alpha   9     widgets Sort new WidgetNameSorter     widgets Sort new WidgetSizeSorter       But Checkout this site for more information    Check it out HERE

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You re going to have to do something like that i think  convert it into a more concrete type    Maybe take it into a List of T rather than ArrayList  so that you get type safety and more options for how you implement the comparer

[c#] Sorting an IList in C#

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