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ObservableCollection(T) Class

ObservableCollection<T> Class

Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed.

System.Object
  System.Collections.ObjectModel.Collection<T>
    System.Collections.ObjectModel.ObservableCollection<T>

Namespace:  System.Collections.ObjectModel
Assemblies:   System.ObjectModel (in System.ObjectModel.dll)
  System (in System.dll)

XMLNS for XAML: Not mapped to an xmlns.

public class ObservableCollection<T> : Collection<T>, 
	INotifyCollectionChanged, INotifyPropertyChanged
See Remarks.

Type Parameters

T

The type of elements in the collection.

The ObservableCollection<T> type exposes the following members.

  NameDescription
Public methodSupported by Portable Class LibraryObservableCollection<T>()Initializes a new instance of the ObservableCollection<T> class.
Public methodSupported by Portable Class LibraryObservableCollection<T>(IEnumerable<T>)Initializes a new instance of the ObservableCollection<T> class that contains elements copied from the specified collection.
Public methodObservableCollection<T>(List<T>)Initializes a new instance of the ObservableCollection<T> class that contains elements copied from the specified list.
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  NameDescription
Public propertySupported by Portable Class LibraryCountGets the number of elements actually contained in the Collection<T>. (Inherited from Collection<T>.)
Public propertySupported by Portable Class LibraryItemGets or sets the element at the specified index. (Inherited from Collection<T>.)
Protected propertySupported by Portable Class LibraryItemsGets a IList<T> wrapper around the Collection<T>. (Inherited from Collection<T>.)
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  NameDescription
Public methodSupported by Portable Class LibraryAddAdds an object to the end of the Collection<T>. (Inherited from Collection<T>.)
Protected methodBlockReentrancyDisallows reentrant attempts to change this collection.
Protected methodCheckReentrancyChecks for reentrant attempts to change this collection.
Public methodSupported by Portable Class LibraryClearRemoves all elements from the Collection<T>. (Inherited from Collection<T>.)
Protected methodSupported by Portable Class LibraryClearItemsRemoves all items from the collection. (Overrides Collection<T>.ClearItems().)
Public methodSupported by Portable Class LibraryContainsDetermines whether an element is in the Collection<T>. (Inherited from Collection<T>.)
Public methodSupported by Portable Class LibraryCopyToCopies the entire Collection<T> to a compatible one-dimensional Array, starting at the specified index of the target array. (Inherited from Collection<T>.)
Public methodSupported by Portable Class LibraryEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodSupported by Portable Class LibraryFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetEnumeratorReturns an enumerator that iterates through the Collection<T>. (Inherited from Collection<T>.)
Public methodSupported by Portable Class LibraryGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodSupported by Portable Class LibraryIndexOfSearches for the specified object and returns the zero-based index of the first occurrence within the entire Collection<T>. (Inherited from Collection<T>.)
Public methodSupported by Portable Class LibraryInsertInserts an element into the Collection<T> at the specified index. (Inherited from Collection<T>.)
Protected methodSupported by Portable Class LibraryInsertItemInserts an item into the collection at the specified index. (Overrides Collection<T>.InsertItem(Int32, T).)
Protected methodSupported by Portable Class LibraryMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodMoveMoves the item at the specified index to a new location in the collection.
Protected methodMoveItemMoves the item at the specified index to a new location in the collection.
Protected methodSupported by Portable Class LibraryOnCollectionChangedRaises the CollectionChanged event with the provided arguments.
Protected methodSupported by Portable Class LibraryOnPropertyChangedRaises the PropertyChanged event with the provided arguments.
Public methodSupported by Portable Class LibraryRemoveRemoves the first occurrence of a specific object from the Collection<T>. (Inherited from Collection<T>.)
Public methodSupported by Portable Class LibraryRemoveAtRemoves the element at the specified index of the Collection<T>. (Inherited from Collection<T>.)
Protected methodSupported by Portable Class LibraryRemoveItemRemoves the item at the specified index of the collection. (Overrides Collection<T>.RemoveItem(Int32).)
Protected methodSupported by Portable Class LibrarySetItemReplaces the element at the specified index. (Overrides Collection<T>.SetItem(Int32, T).)
Public methodSupported by Portable Class LibraryToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Public eventSupported by Portable Class LibraryCollectionChangedOccurs when an item is added, removed, changed, moved, or the entire list is refreshed.
Protected eventSupported by Portable Class LibraryPropertyChangedOccurs when a property value changes.
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  NameDescription
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryICollection.CopyToCopies the elements of the ICollection to an Array, starting at a particular Array index. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate propertySupported by Portable Class LibraryICollection<T>.IsReadOnlyGets a value indicating whether the ICollection<T> is read-only. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate propertySupported by Portable Class LibraryICollection.IsSynchronizedGets a value indicating whether access to the ICollection is synchronized (thread safe). (Inherited from Collection<T>.)
Explicit interface implemetationPrivate propertySupported by Portable Class LibraryICollection.SyncRootGets an object that can be used to synchronize access to the ICollection. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryIEnumerable.GetEnumeratorReturns an enumerator that iterates through a collection. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryIList.AddAdds an item to the IList. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryIList.ContainsDetermines whether the IList contains a specific value. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryIList.IndexOfDetermines the index of a specific item in the IList. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryIList.InsertInserts an item into the IList at the specified index. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate propertySupported by Portable Class LibraryIList.IsFixedSizeGets a value indicating whether the IList has a fixed size. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate propertySupported by Portable Class LibraryIList.IsReadOnlyGets a value indicating whether the IList is read-only. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate propertySupported by Portable Class LibraryIList.ItemGets or sets the element at the specified index. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate methodSupported by Portable Class LibraryIList.RemoveRemoves the first occurrence of a specific object from the IList. (Inherited from Collection<T>.)
Explicit interface implemetationPrivate eventSupported by Portable Class LibraryINotifyPropertyChanged.PropertyChangedOccurs when a property value changes.
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In many cases the data that you work with is a collection of objects. For example, a common scenario in data binding is to use an ItemsControl such as a ListBox, ListView, or TreeView to display a collection of records.

You can enumerate over any collection that implements the IEnumerable interface. However, to set up dynamic bindings so that insertions or deletions in the collection update the UI automatically, the collection must implement the INotifyCollectionChanged interface. This interface exposes the CollectionChanged event, an event that should be raised whenever the underlying collection changes.

WPF provides the ObservableCollection<T> class, which is a built-in implementation of a data collection that implements the INotifyCollectionChanged interface.

Before implementing your own collection, consider using ObservableCollection<T> or one of the existing collection classes, such as List<T>, Collection<T>, and BindingList<T>, among many others. If you have an advanced scenario and want to implement your own collection, consider using IList, which provides a non-generic collection of objects that can be individually accessed by index. Implementing IList provides the best performance with the data binding engine.

NoteNote

To fully support transferring data values from binding source objects to binding targets, each object in your collection that supports bindable properties must implement an appropriate property changed notification mechanism such as the INotifyPropertyChanged interface.

For more information, see "Binding to Collections" in Data Binding Overview.

Notes on XAML Usage

ObservableCollection<T> can be used as a XAML object element in Windows Presentation Foundation (WPF), in versions 3.0 and 3.5. However, the usage has substantial limitations.

  • ObservableCollection<T> must be the root element, because the x:TypeArguments attribute that must be used to specify the constrained type of the generic ObservableCollection<T> is only supported on the object element for the root element.

  • You must declare an x:Class attribute (which entails that the build action for this XAML file must be Page or some other build action that compiles the XAML).

  • ObservableCollection<T> is in a namespace and assembly that are not initially mapped to the default XML namespace. You must map a prefix for the namespace and assembly, and then use that prefix on the object element tag for ObservableCollection<T>.

A more straightforward way to use ObservableCollection<T> capabilities from XAML in an application is to declare your own non-generic custom collection class that derives from ObservableCollection<T>, and constrains it to a specific type. Then map the assembly that contains this class, and reference it as an object element in your XAML.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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