Convert List T to ObservableCollection T in WP7

Question

I don t know if it s just too late or what  but I don t see how to do this     What I m expecting to do  and what the object browser says is there  is this   var oc   new ObservableCollection lt T gt   new List lt T gt         But ObservableCollection lt T gt  has a single parameterless constructor  The object browser says there is 2 overloads where List and IEnuerable should be able to be passed in   Is there something wrong with my setup  Are the constructors not on the phone version   that would be strange   If this really doesn t exist  what is the standard way of doing this with WP7 now

User · Answer

I made an extension so now I can just load a collection with a list by doing:

MyObservableCollection.Load(MyList);

The extension is:

public static class ObservableCollectionExtension
{
  public static ObservableCollection<T> Load<T>(this ObservableCollection<T> Collection, List<T> Source)
  {
          Collection.Clear();    
          Source.ForEach(x => Collection.Add(x));    
          return Collection;
   }
}

User · Answer

ObservableCollection has several constructors which have input parameter of List lt T gt  or IEnumerable lt T gt       List lt T gt  list   new List lt T gt     ObservableCollection lt T gt  collection   new ObservableCollection lt T gt  list

User · Answer

Use this   List lt Class1 gt  myList  ObservableCollection lt Class1 gt  myOC   new ObservableCollection lt Class1 gt  myList

User · Answer

Apparently  your project is targeting Windows Phone 7 0  Unfortunately the constructors that accept IEnumerable lt T gt  or List lt T gt  are not available in WP 7 0  only the parameterless constructor   The other constructors are available in Silverlight 4 and above and WP 7 1 and above  just not in WP 7 0   I guess your only option is to take your list and add the items into a new instance of an ObservableCollection individually as there are no readily available methods to add them in bulk   Though that s not to stop you from putting this into an extension or static method yourself   var list   new List lt SomeType gt                 var oc   new ObservableCollection lt SomeType gt     foreach  var item in list      oc Add item     But don t do this if you don t have to  if you re targeting framework that provides the overloads  then use them

User · Answer

To convert List lt T gt  list to observable collection you may use following code   var oc   new ObservableCollection lt T gt     list ForEach x   gt  oc Add x

User · Answer

ObservableCollection lt FacebookUser WallFeed gt  result   new ObservableCollection lt FacebookUser WallFeed gt  FacebookHelper facebookWallFeeds

User · Answer

The answer provided by Zin Min solved my problem with a single line of code   Excellent   I was having the same issue of converting a generic List to a generic ObservableCollection to use the values from my List to populate a ComboBox that is participating in binding via a factory class for a WPF Window    expediteStatuses   new ObservableCollection lt ExpediteStatus gt   db getExpediteStatuses      Here is the signature for the getExpediteStatuses method   public List lt ExpediteStatus gt  getExpediteStatuses

User · Answer

You ll have to write your own extension method to do this       public static class CollectionEx                  lt summary gt            Copies the contents of an IEnumerable list to an ObservableCollection            lt  summary gt             lt typeparam name  T  gt The type of objects in the source list lt  typeparam gt             lt param name  enumerableList  gt The source list to be converted lt  param gt             lt returns gt An ObservableCollection containing the objects from the source list lt  returns gt        public static ObservableCollection lt T gt  ToObservableCollection lt T gt   this IEnumerable lt T gt  enumerableList                   if  enumerableList    null                  Create an emtpy observable collection object           var observableCollection   new ObservableCollection lt T gt                   Loop through all the records and add to observable collection object           foreach  var item in enumerableList                 observableCollection Add  item                              Return the populated observable collection           return observableCollection                    return null

User · Answer

Extension method from this answer IList lt T gt  to ObservableCollection lt T gt  works pretty well  public static ObservableCollection lt T gt  ToObservableCollection lt T gt  this IEnumerable lt T gt  enumerable      var col   new ObservableCollection lt T gt       foreach   var cur in enumerable         col Add cur         return col

User · Answer

If you are going to be adding lots of items  consider deriving your own class from ObservableCollection and adding items to the protected Items member - this won t raise events in observers   When you are done you can raise the appropriate events   public class BulkUpdateObservableCollection lt T gt    ObservableCollection lt T gt        public void AddRange IEnumerable lt T gt  collection                foreach  var i in collection  Items Add i           OnCollectionChanged new NotifyCollectionChangedEventArgs NotifyCollectionChangedAction Reset            OnPropertyChanged new PropertyChangedEventArgs  Count                When adding many items to an ObservableCollection that is already bound to a UI element  such as LongListSelector  this can make a massive performance difference   Prior to adding the items  you could also ensure you have enough space  so that the list isn t continually being expanded by implementing this method in the BulkObservableCollection class and calling it prior to calling AddRange       public void IncreaseCapacity int increment                var itemsList    List lt T gt  Items          var total   itemsList Count   increment          if  itemsList Capacity  lt  total                        itemsList Capacity   total

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