How to Sort a List T by a property in the object

Question

I have a class called Order which has properties such as OrderId  OrderDate  Quantity  and Total  I have a list of this Order class   List lt Order gt  objListOrder   new List lt Order gt     GetOrderList objListOrder      fill list of orders   Now I want to sort the list based on one property of the Order object  for example I need to sort it by the order date or order id   How can i do this in C

User · Answer

hi just to come back at the question  If you want to sort the List of this sequence   quot 1 quot   quot 10 quot   quot 100 quot   quot 200 quot   quot 2 quot   quot 20 quot   quot 3 quot   quot 30 quot   quot 300 quot  and get the sorted items in this form 1 2 3 10 20 30 100 200 300 you can use this   public class OrderingAscending   IComparer lt String gt                public int Compare String x  String y                        Int32 TryParse x  out var xtmp               Int32 TryParse y  out var ytmp                int comparedItem   xtmp CompareTo ytmp               return comparedItem                   and you can use it in code behind in this form   IComparer lt String gt  comparerHandle   new OrderingAscending     yourList Sort comparerHandle

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An improved of Roger s version   The problem with GetDynamicSortProperty is that only get the property names but what happen if in the GridView we use NavigationProperties  it will send an exception  since it finds null   Example    Employee Company Name    will crash    since allows only  Name  as a parameter to get its value   Here s an improved version that allows us to sort by Navigation Properties   public object GetDynamicSortProperty object item  string propName                try                                        string   prop   propName Split                       Use reflection to get order type                                int i   0                                  while  i  lt  prop Count                                  item   item GetType   GetProperty prop i   GetValue item  null                   i                                                    return item                    catch  Exception ex                        throw ex

User · Answer

From performance point of view the best is to use a sorted list so that data is sorted as it is added to result  Other approaches need at least one extra iteration on data and most create a copy of data so not only performance but memory usage will be affected too  Might not be an issue with couple of hundreds of elements but will be with thousands  especially in services where many concurrent requests may do sorting at the same time  Have a look at System Collections Generic namespace and choose a class with sorting instead of List   And avoid generic implementations using reflection when possible  this can cause performance issues too

User · Answer

To do this without LINQ on  Net2 0   List lt Order gt  objListOrder   GetOrderList    objListOrder Sort      delegate Order p1  Order p2                return p1 OrderDate CompareTo p2 OrderDate              If you re on  Net3 0  then LukeH s answer is what you re after   To sort on multiple properties  you can still do it within a delegate  For example   orderList Sort      delegate Order p1  Order p2                int compareDate   p1 Date CompareTo p2 Date           if  compareDate    0                        return p2 OrderID CompareTo p1 OrderID                     return compareDate             This would give you ascending dates with descending orderIds    However  I wouldn t recommend sticking delegates as it will mean lots of places without code re-use  You should implement an IComparer and just pass that through to your Sort method  See here   public class MyOrderingClass   IComparer lt Order gt        public int Compare Order x  Order y                int compareDate   x Date CompareTo y Date           if  compareDate    0                        return x OrderID CompareTo y OrderID                     return compareDate            And then to use this IComparer class  just instantiate it and pass it to your Sort method   IComparer lt Order gt  comparer   new MyOrderingClass    orderList Sort comparer

User · Answer

Doing it without Linq as you said   public class Order   IComparable       public DateTime OrderDate   get  set        public int OrderId   get  set         public int CompareTo object obj                Order orderToCompare   obj as Order          if  orderToCompare OrderDate  lt  OrderDate    orderToCompare OrderId  lt  OrderId                        return 1                    if  orderToCompare OrderDate  gt  OrderDate    orderToCompare OrderId  gt  OrderId                        return -1                        The orders are equivalent          return 0            Then just call  sort   on your list of Orders

User · Answer

Simplest way to order a list is to use OrderBy   List lt Order gt  objListOrder        source OrderBy order   gt  order OrderDate  ToList      If you want to order by multiple columns like following SQL Query   ORDER BY OrderDate  OrderId   To achieve this you can use ThenBy like following     List lt Order gt  objListOrder        source OrderBy order   gt  order OrderDate  ThenBy order   gt  order OrderId  ToList

User · Answer

Suppose you have the following code  in this code  we have a Passenger class with a couple of properties that we want to sort based on   public class Passenger       public string Name   get        public string LastName   get        public string PassportNo   get        public string Nationality   get         public Passenger string name  string lastName  string passportNo  string nationality                this Name   name          this LastName   lastName          this PassportNo   passportNo          this Nationality   nationality             public static int CompareByName Passenger passenger1  Passenger passenger2                return String Compare passenger1 Name  passenger2 Name              public static int CompareByLastName Passenger passenger1  Passenger passenger2                return String Compare passenger1 LastName  passenger2 LastName              public static int CompareNationality Passenger passenger1  Passenger passenger2                return String Compare passenger1 Nationality  passenger2 Nationality            public class TestPassengerSort       Passenger p1   new Passenger  Johon    Floid    A123456789    USA        Passenger p2   new Passenger  Jo    Sina    A987463215    UAE        Passenger p3   new Passenger  Ped    Zoola    A987855215    Italy         public void SortThem                 Passenger   passengers   new Passenger     p1  p2  p3            List lt Passenger gt  passengerList   new List lt Passenger gt    p1  p2  p3             Array Sort passengers  Passenger CompareByName           Array Sort passengers  Passenger CompareByLastName           Array Sort passengers  Passenger CompareNationality            passengerList Sort Passenger CompareByName           passengerList Sort Passenger CompareByLastName           passengerList Sort Passenger CompareNationality              So you can implement your sort structure by using Composition delegate

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Get data from database  then sort list by staff name   List lt StaffMember gt  staffList   staffHandler GetStaffMembers     var sortedList   from staffmember in staffList                  orderby staffmember Name ascending                  select staffmember

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Using LINQ  objListOrder   GetOrderList                       OrderBy o   gt  o OrderDate                      ToList     objListOrder   GetOrderList                       OrderBy o   gt  o OrderId                      ToList

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Please let me complete the answer by  LukeH with some sample code  as I have tested it I believe it may be useful for some   public class Order       public string OrderId   get  set        public DateTime OrderDate   get  set        public int Quantity   get  set        public int Total   get  set         public Order string orderId  DateTime orderDate  int quantity  int total                OrderId   orderId          OrderDate   orderDate          Quantity   quantity          Total   total           public void SampleDataAndTest         List lt Order gt  objListOrder   new List lt Order gt          objListOrder Add new Order  tu me paulo    Convert ToDateTime  01 06 2016    1  44        objListOrder Add new Order  ante laudabas   Convert ToDateTime  02 05 2016    2  55        objListOrder Add new Order  ad ordinem    Convert ToDateTime  03 04 2016    5  66        objListOrder Add new Order  collocationem    Convert ToDateTime  04 03 2016    9  77        objListOrder Add new Order  que rerum ac    Convert ToDateTime  05 02 2016    10  65        objListOrder Add new Order  locorum   cuius   Convert ToDateTime  06 01 2016    1  343          Console WriteLine  Sort the list by date ascending         objListOrder Sort  x  y    gt  x OrderDate CompareTo y OrderDate         foreach  Order o in objListOrder          Console WriteLine  OrderId       o OrderId     OrderDate       o OrderDate ToString       Quantity       o Quantity     Total       o Total        Console WriteLine  Sort the list by date descending         objListOrder Sort  x  y    gt  y OrderDate CompareTo x OrderDate        foreach  Order o in objListOrder          Console WriteLine  OrderId       o OrderId     OrderDate       o OrderDate ToString       Quantity       o Quantity     Total       o Total        Console WriteLine  Sort the list by OrderId ascending         objListOrder Sort  x  y    gt  x OrderId CompareTo y OrderId        foreach  Order o in objListOrder          Console WriteLine  OrderId       o OrderId     OrderDate       o OrderDate ToString       Quantity       o Quantity     Total       o Total          etc

User · Answer

var obj   db Items Where     var orderBYItemId   obj OrderByDescending c   gt  Convert ToInt32 c ID

User · Answer

A Classical Object Oriented Solution  First I must genuflect to the awesomeness of LINQ      Now that we ve got that out of the way  A variation on JimmyHoffa answer  With generics the CompareTo parameter becomes type safe   public class Order   IComparable lt Order gt         public int CompareTo  Order that             if   that    null   return 1          if   this OrderDate  gt  that OrderDate  return 1          if   this OrderDate  lt  that OrderDate  return -1          return 0              in the client code    assume myOrders is a populated List lt Order gt  myOrders Sort       This default sortability is re-usable of course  That is each client does not have to redundantly re-write the sorting logic  Swapping the  1  and  -1   or the logic operators  your choice  reverses the sort order

User · Answer

You can do something more generic about the properties selection yet be specific about the type you re selecting from  in your case  Order    write your function as a generic one   public List lt Order gt  GetOrderList lt T gt  IEnumerable lt Order gt  orders  Func lt Order  T gt  propertySelector                        return  from order in orders                     orderby propertySelector order                      select order  ToList                 and then use it like this   var ordersOrderedByDate   GetOrderList orders  x   gt  x OrderDate     You can be even more generic and define an open type for what you want to order   public List lt T gt  OrderBy lt T P gt  IEnumerable lt T gt  collection  Func lt T P gt  propertySelector                        return  from item in collection                     orderby propertySelector item                      select item  ToList                 and use it the same way   var ordersOrderedByDate   OrderBy orders  x   gt  x OrderDate     Which is a stupid unnecessary complex way of doing a LINQ style  OrderBy   But it may give you a clue of how it can be implemented in a generic way

User · Answer

Anybody working with nullable types  Value is required to use CompareTo   objListOrder Sort  x  y    gt  x YourNullableType Value CompareTo y YourNullableType Value

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Totally generic sorting for use with a gridview  public List lt T gt  Sort List lt T gt  string sortDirection  string sortExpression  List lt T gt  data                 List lt T gt  data sorted   new List lt T gt              if  sortDirection     Ascending                         data sorted    from n in data                               orderby GetDynamicSortProperty n  sortExpression  ascending                               select n  ToList                      else if  sortDirection     Descending                         data sorted    from n in data                               orderby GetDynamicSortProperty n  sortExpression  descending                               select n  ToList                        return data sorted              public object GetDynamicSortProperty object item  string propName                  Use reflection to get order type         return item GetType   GetProperty propName  GetValue item  null

User · Answer

Make use of LiNQ OrderBy   List lt Order gt  objListOrder new List lt Order gt          objListOrder GetOrderList   OrderBy o  gt o orderid  ToList

User · Answer

None of the above answers were generic enough for me so I made this one   var someUserInputStringValue    propertyNameOfObject i e   Quantity  or  Date    var SortedData   DataToBeSorted                     OrderBy m   gt  m GetType                                      GetProperties                                      First n   gt                                         n Name    someUserInputStringValue                      GetValue m  null                     ToList      Careful on massive data sets though  It s easy code but could get you in trouble if the collection is huge and the object type of the collection has a large number of fields  Run time is NxM where   N     of Elements in collection  M     of Properties within Object

User · Answer

Based on GenericTypeTea s Comparer   we can obtain more flexibility by adding sorting flags      public class MyOrderingClass   IComparer lt Order gt          public int Compare Order x  Order y              int compareDate   x Date CompareTo y Date             if  compareDate    0                  int compareOrderId   x OrderID CompareTo y OrderID                  if  OrderIdDescending                      compareOrderId   -compareOrderId                                return compareOrderId                         if  DateDescending                  compareDate   -compareDate                        return compareDate                 public bool DateDescending   get  set          public bool OrderIdDescending   get  set            In this scenario  you must instantiate it as MyOrderingClass explicitly  rather then IComparer   in order to set its sorting properties       MyOrderingClass comparer   new MyOrderingClass      comparer DateDescending          comparer OrderIdDescending          orderList Sort comparer

User · Answer

If you need to sort the list in-place then you can use the Sort method  passing a Comparison lt T gt  delegate   objListOrder Sort  x  y    gt  x OrderDate CompareTo y OrderDate      If you prefer to create a new  sorted sequence rather than sort in-place then you can use LINQ s OrderBy method  as mentioned in the other answers

User · Answer

Here is a generic LINQ extension method that does not create an extra copy of the list   public static void Sort lt T U gt  this List lt T gt  list  Func lt T  U gt  expression      where U   IComparable lt U gt        list Sort  x  y    gt  expression Invoke x  CompareTo expression Invoke y         To use it   myList Sort x  gt  x myProperty     I recently built this additional one which accepts an ICompare lt U gt   so that you can customize the comparison   This came in handy when I needed to do a Natural string sort   public static void Sort lt T  U gt  this List lt T gt  list  Func lt T  U gt  expression  IComparer lt U gt  comparer      where U   IComparable lt U gt            list Sort  x  y    gt  comparer Compare expression Invoke x   expression Invoke y

User · Answer

The easiest way I can think of is to use Linq   List lt Order gt  SortedList   objListOrder OrderBy o  gt o OrderDate  ToList

[c#] How to Sort a List<T> by a property in the object

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