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Dictionary<TKey,TValue>.KeyCollection.Enumerator Struct

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Definition

Namespace:
System.Collections.Generic
Assembly:
System.Collections.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
Dictionary.cs
Source:
Dictionary.cs
Source:
Dictionary.cs

Enumerates the elements of a Dictionary<TKey,TValue>.KeyCollection.

public: value class Dictionary<TKey, TValue>::KeyCollection::Enumerator : System::Collections::Generic::IEnumerator<TKey>
public struct Dictionary<TKey,TValue>.KeyCollection.Enumerator : System.Collections.Generic.IEnumerator<TKey>
[System.Serializable]
public struct Dictionary<TKey,TValue>.KeyCollection.Enumerator : System.Collections.Generic.IEnumerator<TKey>
type Dictionary<'Key, 'Value>.KeyCollection.Enumerator = struct
    interface IEnumerator<'Key>
    interface IEnumerator
    interface IDisposable
[<System.Serializable>]
type Dictionary<'Key, 'Value>.KeyCollection.Enumerator = struct
    interface IEnumerator<'Key>
    interface IDisposable
    interface IEnumerator
Public Structure Dictionary(Of TKey, TValue).KeyCollection.Enumerator
Implements IEnumerator(Of TKey)

Type Parameters

TKey
TValue
Inheritance
Object
ValueType
Dictionary<TKey,TValue>.KeyCollection.Enumerator
Attributes
SerializableAttribute
Implements
IEnumerator<TKey> IEnumerator IDisposable

Remarks

The foreach statement of the C# language (for each in C++, For Each in Visual Basic) hides the complexity of enumerators. Therefore, using foreach is recommended, instead of directly manipulating the enumerator.

Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.

Initially, the enumerator is positioned before the first element in the collection. At this position, Current is undefined. You must call MoveNext to advance the enumerator to the first element of the collection before reading the value of Current.

Current returns the same object until MoveNext is called. MoveNext sets Current to the next element.

If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. When the enumerator is at this position, subsequent calls to MoveNext also return false. If the last call to MoveNext returned false, Current is undefined. You cannot set Current to the first element of the collection again; you must create a new enumerator instance instead.

An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding elements or changing the capacity, the enumerator is irrecoverably invalidated and the next call to MoveNext or IEnumerator.Reset throws an InvalidOperationException.

.NET Core 3.0+ only: The only mutating methods which do not invalidate enumerators are Remove and Clear.

The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

Default implementations of collections in System.Collections.Generic are not synchronized.

Properties

Current

Gets the element at the current position of the enumerator.

Methods

Dispose()

Releases all resources used by the Dictionary<TKey,TValue>.KeyCollection.Enumerator.
MoveNext()

Advances the enumerator to the next element of the Dictionary<TKey,TValue>.KeyCollection.

Explicit Interface Implementations

IEnumerator.Current

Gets the element at the current position of the enumerator.
IEnumerator.Reset()

Sets the enumerator to its initial position, which is before the first element in the collection.

Applies to

See also