CachedDataItemEnumerator Class

Статья
07/25/2011

Iterates through a CachedDataItemCollection.

Inheritance Hierarchy

System.Object
Microsoft.VisualStudio.Tools.Applications.CachedDataItemEnumerator

Namespace: Microsoft.VisualStudio.Tools.Applications
Assembly: Microsoft.VisualStudio.Tools.Applications.ServerDocument (in Microsoft.VisualStudio.Tools.Applications.ServerDocument.dll)

Syntax

'Declaration
<PermissionSetAttribute(SecurityAction.Demand, Name := "FullTrust")> _
Public NotInheritable Class CachedDataItemEnumerator _
    Implements IEnumerator(Of CachedDataItem), IDisposable,  _
    IEnumerator

[PermissionSetAttribute(SecurityAction.Demand, Name = "FullTrust")]
public sealed class CachedDataItemEnumerator : IEnumerator<CachedDataItem>, 
    IDisposable, IEnumerator

The CachedDataItemEnumerator type exposes the following members.

Properties

	Name	Description
	Current	Gets the CachedDataItem at the current position of the enumerator.

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Methods

	Name	Description
	Equals	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	MoveNext	Advances the enumerator to the next CachedDataItem in the CachedDataItemCollection.
	Reset	Sets the enumerator to its initial position, which is before the first CachedDataItem in the collection.
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Explicit Interface Implementations

	Name	Description
	IEnumerator.Current	For a description of this member, see Current.
	IDisposable.Dispose	Releases all resources used by the CachedDataItemEnumerator.

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Remarks

Visual Basic and C# each contain a statement that hides the complexity of the enumerators (foreach in C# and For Each in Visual Basic). Use the appropriate statement for the language you are using, 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. The Reset method also brings the enumerator back to this position. At this position, setting the Current property throws an exception. Therefore, you must call the MoveNext method to advance the enumerator to the first element of the collection before reading the value of Current.

Current returns the same object until either MoveNext or Reset 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, calling Current throws an exception. To set Current to the first element of the collection again, you can call Reset followed by MoveNext.

An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and the next call to MoveNext or Reset throws an InvalidOperationException. If the collection is modified between MoveNext and Current, Current returns the element that it is set to, even if the enumerator is already invalidated.

The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

Thread Safety

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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