ObservableCollection<T> ObservableCollection<T> ObservableCollection<T> ObservableCollection<T> Class

Definition

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

generic <typename T>
public ref class ObservableCollection : System::Collections::ObjectModel::Collection<T>, System::Collections::Specialized::INotifyCollectionChanged, System::ComponentModel::INotifyPropertyChanged
[System.Serializable]
public class ObservableCollection<T> : System.Collections.ObjectModel.Collection<T>, System.Collections.Specialized.INotifyCollectionChanged, System.ComponentModel.INotifyPropertyChanged
type ObservableCollection<'T> = class
    inherit Collection<'T>
    interface INotifyCollectionChanged
    interface INotifyPropertyChanged
Public Class ObservableCollection(Of T)
Inherits Collection(Of T)
Implements INotifyCollectionChanged, INotifyPropertyChanged

Type Parameters

T

The type of elements in the collection.

Inheritance
ObservableCollection<T>ObservableCollection<T>ObservableCollection<T>ObservableCollection<T>
Derived
Attributes
Implements

Remarks

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.

Note

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.

Constructors

ObservableCollection<T>() ObservableCollection<T>() ObservableCollection<T>() ObservableCollection<T>()

Initializes a new instance of the ObservableCollection<T> class.

ObservableCollection<T>(IEnumerable<T>) ObservableCollection<T>(IEnumerable<T>) ObservableCollection<T>(IEnumerable<T>) ObservableCollection<T>(IEnumerable<T>)

Initializes a new instance of the ObservableCollection<T> class that contains elements copied from the specified collection.

ObservableCollection<T>(List<T>) ObservableCollection<T>(List<T>) ObservableCollection<T>(List<T>) ObservableCollection<T>(List<T>)

Initializes a new instance of the ObservableCollection<T> class that contains elements copied from the specified list.

Methods

Add(T) Add(T) Add(T) Add(T)

Adds an object to the end of the Collection<T>.

(Inherited from Collection<T>)
BlockReentrancy() BlockReentrancy() BlockReentrancy() BlockReentrancy()

Disallows reentrant attempts to change this collection.

CheckReentrancy() CheckReentrancy() CheckReentrancy() CheckReentrancy()

Checks for reentrant attempts to change this collection.

Clear() Clear() Clear() Clear()

Removes all elements from the Collection<T>.

(Inherited from Collection<T>)
ClearItems() ClearItems() ClearItems() ClearItems()

Removes all items from the collection.

Contains(T) Contains(T) Contains(T) Contains(T)

Determines whether an element is in the Collection<T>.

(Inherited from Collection<T>)
CopyTo(T[], Int32) CopyTo(T[], Int32) CopyTo(T[], Int32) CopyTo(T[], Int32)

Copies the entire Collection<T> to a compatible one-dimensional Array, starting at the specified index of the target array.

(Inherited from Collection<T>)
Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetEnumerator() GetEnumerator() GetEnumerator() GetEnumerator()

Returns an enumerator that iterates through the Collection<T>.

(Inherited from Collection<T>)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Gets the Type of the current instance.

(Inherited from Object)
IndexOf(T) IndexOf(T) IndexOf(T) IndexOf(T)

Searches for the specified object and returns the zero-based index of the first occurrence within the entire Collection<T>.

(Inherited from Collection<T>)
Insert(Int32, T) Insert(Int32, T) Insert(Int32, T) Insert(Int32, T)

Inserts an element into the Collection<T> at the specified index.

(Inherited from Collection<T>)
InsertItem(Int32, T) InsertItem(Int32, T) InsertItem(Int32, T) InsertItem(Int32, T)

Inserts an item into the collection at the specified index.

MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
Move(Int32, Int32) Move(Int32, Int32) Move(Int32, Int32) Move(Int32, Int32)

Moves the item at the specified index to a new location in the collection.

MoveItem(Int32, Int32) MoveItem(Int32, Int32) MoveItem(Int32, Int32) MoveItem(Int32, Int32)

Moves the item at the specified index to a new location in the collection.

OnCollectionChanged(NotifyCollectionChangedEventArgs) OnCollectionChanged(NotifyCollectionChangedEventArgs) OnCollectionChanged(NotifyCollectionChangedEventArgs) OnCollectionChanged(NotifyCollectionChangedEventArgs)

Raises the CollectionChanged event with the provided arguments.

OnPropertyChanged(PropertyChangedEventArgs) OnPropertyChanged(PropertyChangedEventArgs) OnPropertyChanged(PropertyChangedEventArgs) OnPropertyChanged(PropertyChangedEventArgs)

Raises the PropertyChanged event with the provided arguments.

Remove(T) Remove(T) Remove(T) Remove(T)

Removes the first occurrence of a specific object from the Collection<T>.

(Inherited from Collection<T>)
RemoveAt(Int32) RemoveAt(Int32) RemoveAt(Int32) RemoveAt(Int32)

Removes the element at the specified index of the Collection<T>.

(Inherited from Collection<T>)
RemoveItem(Int32) RemoveItem(Int32) RemoveItem(Int32) RemoveItem(Int32)

Removes the item at the specified index of the collection.

SetItem(Int32, T) SetItem(Int32, T) SetItem(Int32, T) SetItem(Int32, T)

Replaces the element at the specified index.

ToString() ToString() ToString() ToString()

Returns a string that represents the current object.

(Inherited from Object)

Events

CollectionChanged CollectionChanged CollectionChanged CollectionChanged

Occurs when an item is added, removed, changed, moved, or the entire list is refreshed.

PropertyChanged PropertyChanged PropertyChanged PropertyChanged

Occurs when a property value changes.

Explicit Interface Implementations

ICollection.CopyTo(Array, Int32) ICollection.CopyTo(Array, Int32) ICollection.CopyTo(Array, Int32) ICollection.CopyTo(Array, Int32)

Copies the elements of the ICollection to an Array, starting at a particular Array index.

(Inherited from Collection<T>)
IEnumerable.GetEnumerator() IEnumerable.GetEnumerator() IEnumerable.GetEnumerator() IEnumerable.GetEnumerator()

Returns an enumerator that iterates through a collection.

(Inherited from Collection<T>)
IList.Add(Object) IList.Add(Object) IList.Add(Object) IList.Add(Object)

Adds an item to the IList.

(Inherited from Collection<T>)
IList.Contains(Object) IList.Contains(Object) IList.Contains(Object) IList.Contains(Object)

Determines whether the IList contains a specific value.

(Inherited from Collection<T>)
IList.IndexOf(Object) IList.IndexOf(Object) IList.IndexOf(Object) IList.IndexOf(Object)

Determines the index of a specific item in the IList.

(Inherited from Collection<T>)
IList.Insert(Int32, Object) IList.Insert(Int32, Object) IList.Insert(Int32, Object) IList.Insert(Int32, Object)

Inserts an item into the IList at the specified index.

(Inherited from Collection<T>)
IList.Remove(Object) IList.Remove(Object) IList.Remove(Object) IList.Remove(Object)

Removes the first occurrence of a specific object from the IList.

(Inherited from Collection<T>)
INotifyPropertyChanged.PropertyChanged INotifyPropertyChanged.PropertyChanged INotifyPropertyChanged.PropertyChanged INotifyPropertyChanged.PropertyChanged

Occurs when a property value changes.

Properties

Count Count Count Count

Gets the number of elements actually contained in the Collection<T>.

(Inherited from Collection<T>)
ICollection.IsSynchronized ICollection.IsSynchronized ICollection.IsSynchronized ICollection.IsSynchronized

Gets a value indicating whether access to the ICollection is synchronized (thread safe).

(Inherited from Collection<T>)
ICollection.SyncRoot ICollection.SyncRoot ICollection.SyncRoot ICollection.SyncRoot

Gets an object that can be used to synchronize access to the ICollection.

(Inherited from Collection<T>)
ICollection<T>.IsReadOnly ICollection<T>.IsReadOnly ICollection<T>.IsReadOnly ICollection<T>.IsReadOnly

Gets a value indicating whether the ICollection<T> is read-only.

(Inherited from Collection<T>)
IList.IsFixedSize IList.IsFixedSize IList.IsFixedSize IList.IsFixedSize

Gets a value indicating whether the IList has a fixed size.

(Inherited from Collection<T>)
IList.IsReadOnly IList.IsReadOnly IList.IsReadOnly IList.IsReadOnly

Gets a value indicating whether the IList is read-only.

(Inherited from Collection<T>)
IList.Item[Int32] IList.Item[Int32] IList.Item[Int32] IList.Item[Int32]

Gets or sets the element at the specified index.

(Inherited from Collection<T>)
Items Items Items Items

Gets a IList<T> wrapper around the Collection<T>.

(Inherited from Collection<T>)
Item[Int32] Item[Int32] Item[Int32] Item[Int32]

Gets or sets the element at the specified index.

(Inherited from Collection<T>)

Extension Methods

CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>)

Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable)

Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable)

Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable)

Enables parallelization of a query.

AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable)

Converts an IEnumerable to an IQueryable.

Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>)

Returns a collection of elements that contains the ancestors of every node in the source collection.

Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName)

Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.

DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>)

Returns a collection of the descendant nodes of every document and element in the source collection.

Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>)

Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName)

Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>)

Returns a collection of the child elements of every element and document in the source collection.

Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName)

Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>)

Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.

Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>)

Returns a collection of the child nodes of every document and element in the source collection.

Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>)

Removes every node in the source collection from its parent node.

Applies to

See also