Sort a Custom Class List T

Question

I would like to sort my list with the date property  This is my custom class  using System  using System Collections Generic  using System Linq  using System Web   namespace Test Web       public class cTag               public int id   get  set            public int regnumber   get  set            public string date   get  set             An this is the List that I want to sort  List lt cTag gt  Week   new List lt cTag gt      I want to sort the List by the date property of the cTag class  The date is in the format dd MM yyyy  I read something about the IComparable interface  but I don t know how to use it

User · Answer

First things first  if the date property is storing a date  store it using a DateTime  If you parse the date through the sort you have to parse it for each item being compared  that s not very efficient     You can then make an IComparer   public class TagComparer   IComparer lt cTag gt        public int Compare cTag first  cTag second                if  first    null  amp  amp  second    null                           We can compare both properties              return first date CompareTo second date                      if  first    null  amp  amp  second    null                           We can t compare any properties  so they are essentially equal              return 0                     if  first    null                           Only the first instance is not null  so prefer that              return -1                        Only the second instance is not null  so prefer that          return 1           var list   new List lt cTag gt        populate list   list Sort new TagComparer       You can even do it as a delegate   list Sort  first  second    gt                            if  first    null  amp  amp  second    null                    return first date CompareTo second date                  if  first    null  amp  amp  second    null                    return 0                 if  first    null                    return -1                 return 1

User · Answer

Thanks for all the fast Answers   This is my solution   Week Sort delegate cTag c1  cTag c2    return DateTime Parse c1 date  CompareTo DateTime Parse c2 date          Thanks

User · Answer

One way to do this is with a delegate  List lt cTag gt  week   new List lt cTag gt        add some stuff to the list    now sort week Sort delegate cTag c1  cTag c2    return c1 date CompareTo c2 date

User · Answer

You are right - you need to implement IComparable  To do this  simply declare your class   public MyClass   IComparable     int IComparable CompareTo object obj              In CompareTo  you just implement your custom comparison algorithm  you can use DateTime objects to do this  but just be certain to check the type of  obj  first   For further information  see here and here

User · Answer

look at overloaded Sort method of the List class  there are some ways to to it  one of them  your custom class has to implement IComparable interface then you cam use Sort method of the List class

User · Answer

YourVariable Sort  a  b    gt  a amount CompareTo b amount

User · Answer

List lt cTag gt  week   new List lt cTag gt     week Sort  x  y    gt       DateTime ParseExact x date   dd MM yyyy   CultureInfo InvariantCulture  CompareTo      DateTime ParseExact y date   dd MM yyyy   CultureInfo InvariantCulture

User · Answer

You can use linq   var q   from tag in Week orderby Convert ToDateTime tag date  select tag  List lt cTag gt  Sorted   q ToList

User · Answer

You are correct that your cTag class must implement IComparable lt T gt  interface  Then you can just call Sort   on your list   To implement IComparable lt T gt  interface  you must implement CompareTo T other  method  The easiest way to do this is to call CompareTo method of the field you want to compare  which in your case is date   public class cTag IComparable lt cTag gt        public int id   get  set        public int regnumber   get  set        public string date   get  set        public int CompareTo cTag other            return date CompareTo other date             However  this wouldn t sort well  because this would use classic sorting on strings  since you declared date as string   So I think the best think to do would be to redefine the class and to declare date not as string  but as DateTime  The code would stay almost the same   public class cTag IComparable lt cTag gt        public int id   get  set        public int regnumber   get  set        public DateTime date   get  set        public int CompareTo cTag other            return date CompareTo other date             Only thing you d have to do when creating the instance of the class to convert your string containing the date into DateTime type  but it can be done easily e g  by DateTime Parse String  method

User · Answer

For this case you can also sort using LINQ   week   week OrderBy w   gt  DateTime Parse w date   ToList

[c#] Sort a Custom Class List<T>

Examples related to c#

Examples related to sorting