mscorlib
BCL
Implemented by classes that support a simple iteration over a collection.
[Note: IEnumerator contains the System.Collections.IEnumerator.MoveNext and System.Collections.IEnumerator.Reset methods and the System.Collections.IEnumerator.Current property. The consumer of an object should call these methods or use this property when iterating over or reading the elements of a collection.When an enumerator is instantiated or a call is made to System.Collections.IEnumerator.Reset, the enumerator is positioned immediately before the first element of the collection and a snapshot of the collection is taken. When the enumerator is in this position, a call to System.Collections.IEnumerator.MoveNext is necessary before reading System.Collections.IEnumerator.Current from the collection. If changes are made to the collection, such as adding, modifying or deleting elements, the snapshot gets out of sync and the enumerator throws a InvalidOperationException. Two enumerators instantiated from the same collection at the same time can have different snapshots of the collection.
Enumerators are intended to be used only to read data in the collection.
An enumerator does not have exclusive access to the collection for which it was instantiated.
]
System.Collections Namespace
IEnumerator Methods
IEnumerator.MoveNext Method
IEnumerator.Reset Method
IEnumerator Properties
Advances the current instance to the next element of the collection.
trueif the current instance was successfully advanced to the next element;falseif the current instance has passed the end of the collection.
Exception Type Condition InvalidOperationException The collection was modified after the current instance was instantiated.
[Note: When the current instance is constructed or after System.Collections.IEnumerator.Reset is called, the current instance is positioned immediately before the first element of the collection. Use System.Collections.IEnumerator.MoveNext to position it over the first element of the collection.]
[Behaviors: A call to System.Collections.IEnumerator.MoveNext is required to position the current instance over the next element in the collection and return
trueif the current instance was not positioned beyond the last element of the collection when System.Collections.IEnumerator.MoveNext was called. If the current instance is already positioned immediately after the last element of the collection, a call to System.Collections.IEnumerator.MoveNext is required to returnfalse, and the current instance is required to remain in the same position. If elements are added, removed, or repositioned in the collection after the current instance was instantiated, it is required that a call to System.Collections.IEnumerator.MoveNext throw InvalidOperationException.]
[Usage: Use the System.Collections.IEnumerator.MoveNext method to check if the current instance is positioned immediately after the last element of the collection, and to position it over the next element if it is not already past the last element of the collection. This allows the use of a conditional loop to iterate over the entire collection.]
System.Collections.IEnumerator Interface, System.Collections Namespace
Positions the enumerator immediately before the first element in the collection.
Exception Type Condition InvalidOperationException The collection was modified after the enumerator was instantiated.
[Note: When the current instance is constructed or after System.Collections.IEnumerator.Reset is called, the current instance is positioned immediately before the first element of the collection, use System.Collections.IEnumerator.MoveNext to position the current instance over the first element of the collection. ]
[Behaviors: A call to System.Collections.IEnumerator.Reset is required to position the current instance immediately before the first element of the collection. If elements are added, removed, or repositioned in the collection after the current instance was instantiated, it is required that a call to System.Collections.IEnumerator.Reset throw a InvalidOperationException.]
[Overrides: A call to System.Collections.IEnumerator.Reset can involve taking a new snapshot of the collection or simply moving to the beginning of the collection. The preferred implementation is to simply move the current instance to the beginning of the collection, before the first element. This invalidates the current instance if the collection has been modified since the current instance was constructed, which is consistent with System.Collections.IEnumerator.MoveNext and System.Collections.IEnumerator.Current.]
[Usage: Use the System.Collections.IEnumerator.MoveNext method to check if the current instance is positioned immediately past the last element of the collection, and to position it over the next element if it is not already past the last element of the collection.]
System.Collections.IEnumerator Interface, System.Collections Namespace
object Current { get; }
Gets the element in the collection over which the current instance is positioned.
The element in the collection over which the current instance is positioned.
Exception Type Condition InvalidOperationException The current instance is positioned before the first element or after the last element of the collection. The collection was modified after the current instance was instantiated.
[Note: When the current instance is constructed or after System.Collections.IEnumerator.Reset is called, use System.Collections.IEnumerator.MoveNext to position the current instance over the first element of the collection. ]
[Behaviors: It is required that System.Collections.IEnumerator.Current return the element in the collection over which the current instance is positioned unless it is positioned before the first or after the last element of the collection. If the current instance is positioned before the first element or after the last element of the collection, or elements were added, removed, or repositioned in the collection after the current instance was instantiated, System.Collections.IEnumerator.Current is required to throw InvalidOperationException.
It is also required that System.Collections.IEnumerator.Current not change the position of the current instance: consecutive calls to System.Collections.IEnumerator.Current are required to return the same object until either System.Collections.IEnumerator.MoveNext or System.Collections.IEnumerator.Reset is called.
This property is read-only.
]
[Usage: Use System.Collections.IEnumerator.Current to get the element in the collection over which the current instance is positioned, provided that the current instance is not positioned before the first element or after the last element of the collection.]
System.Collections.IEnumerator Interface, System.Collections Namespace