Class CacheItem

Class that represents a cached item including its dependencies, expiration and eviction information

Inheritance

System.Object

CacheItem

Namespace:

Assembly: Alachisoft.NCache.Web.dll

Syntax

public class CacheItem : ICloneable

Examples

You can create an instance of CacheItem class and Add(String, Object) it to the Cache

object someData = new object();
CacheItem item = new CacheItem(someData);
item.SlidingExpiration = new TimeSpan(0,5,0);
item.Priority = CacheItemPriority.High;
item.ItemRemoveCallback = onRemove;
Cache cache = NCache.InitializeCache("myCache");
cache.Add("someData", item);

Constructors

CacheItem(Object)

Costructor

Declaration

public CacheItem(object value)

Parameters

Type	Name	Description
System.Object	value	Actual object to be stored in cache

Properties

AbsoluteExpiration

The time at which the added object expires and is removed from the cache.

Declaration

public DateTime AbsoluteExpiration { get; set; }

Property Value

Type	Description
System.DateTime	The default value is Cache.NoAbsoluteExpiration

Remarks

You cannot set both sliding and absolute expirations on the same cached item. If you do so, an System.ArgumentException is thrown when you will try to add or insert the CacheItem.

AsyncItemAddCallback

A delegate that, if provided, is called when an Asynchronous request for Add Operation completes. You can use this to obtain the results of an 'AddAsync' operation.

Declaration

public AsyncItemAddedCallback AsyncItemAddCallback { get; set; }

Property Value

Type	Description
AsyncItemAddedCallback

AsyncItemUpdateCallback

A delegate that, if provided, is called when an Asynchronous request for Update Operation completes. You can use this to obtain the results of an 'InsertAsync' operation.

Declaration

public AsyncItemUpdatedCallback AsyncItemUpdateCallback { get; set; }

Property Value

Type	Description
AsyncItemUpdatedCallback

CreationTime

Get the cache item creation time

Declaration

public DateTime CreationTime { get; }

Property Value

Type	Description
System.DateTime

Dependency

The file or cache key dependencies for the item. When any dependency changes, the object becomes invalid and is removed from the cache. If there are no dependencies, this property contains a null reference (Nothing in Visual Basic).

Declaration

public CacheDependency Dependency { get; set; }

Property Value

Type	Description
CacheDependency

Group

The name of the group to associate with the cache item. All cache items with the same group name are logically grouped together.

Declaration

public string Group { get; set; }

Property Value

Type	Description
System.String

IsResyncExpiredItems

Gets/Sets a value indicating whether the object when expired will cause a refetch of the object from the master datasource. (Resync Expired Items)

Declaration

public bool IsResyncExpiredItems { get; set; }

Property Value

Type	Description
System.Boolean	true if "Resync Expired Items" on this object has been set; otherwise, false. The default is false.

Remarks

Whenever an expired item is fectched from the cache it is read thru the datasource. If the item is not available in the datasource the item is removed from the cache and null value is returned.

Note: For "Resync Expired Items" to work you must a specify read through provider for the cache. For more information on read through providers see online documentation.

ItemRemoveCallback

A delegate that, if provided, is called when an object is removed from the cache. You can use this to notify applications when their objects are deleted from the cache.

Declaration

[Obsolete("This delegate is deprecated. 'Please use SetCacheDataNotification(CacheDataNotificationCallback callback, EventType eventType, EventDataFilter datafilter)'", false)]
public CacheItemRemovedCallback ItemRemoveCallback { get; set; }

Property Value

Type	Description
CacheItemRemovedCallback

ItemUpdateCallback

A delegate that, if provided, is called when an object is updated in the cache. You can use this to notify applications when their objects are updated in the cache.

Declaration

[Obsolete("This delegate is deprecated. 'Please use SetCacheDataNotification(CacheDataNotificationCallback callback, EventType eventType, EventDataFilter datafilter)'", false)]
public CacheItemUpdatedCallback ItemUpdateCallback { get; set; }

Property Value

Type	Description
CacheItemUpdatedCallback

LastModifiedTime

Get the cache item last modified time

Declaration

public DateTime LastModifiedTime { get; }

Property Value

Type	Description
System.DateTime

NamedTags

Get or set the named tags

Declaration

public NamedTagsDictionary NamedTags { get; set; }

Property Value

Type	Description
NamedTagsDictionary

Priority

The relative cost of the object, as expressed by the enumeration. The cache uses this value when it evicts objects; objects with a lower cost are removed from the cache before objects with a higher cost.

Declaration

public CacheItemPriority Priority { get; set; }

Property Value

Type	Description
CacheItemPriority	The default value is CacheItemPriority.Default.

Remarks

This property will be used only when the eviction policy is set to priority in the configuration.

ResyncProviderName

Gets/Sets Provider name for re-synchronization of cache

Declaration

public string ResyncProviderName { get; set; }

Property Value

Type	Description
System.String

SlidingExpiration

The interval between the time the added object was last accessed and when that object expires. If this value is the equivalent of 20 minutes, the object expires and is removed from the cache 20 minutes after it is last accessed.

Declaration

public TimeSpan SlidingExpiration { get; set; }

Property Value

Type	Description
System.TimeSpan	The default value is Cache.NoSlidingExpiration.

Remarks

If the slidingExpiration property is set to NoSlidingExpiration, sliding expiration is disabled. If you set the slidingExpiration parameter to less than System.TimeSpan.Zero, or the equivalent of more than one year, an System.ArgumentOutOfRangeException is thrown when you will try to add or insert the CacheItem. You cannot set both sliding and absolute expirations on the same cached item. If you do so, an System.ArgumentException is thrown when you will try to add or insert the CacheItem.

SubGroup

The name of the sub-group within a group. This hierarchical grouping gives more control over the cache items.

Declaration

public string SubGroup { get; set; }

Property Value

Type	Description
System.String

SyncDependency

CacheSyncDependency for this item.

Declaration

public CacheSyncDependency SyncDependency { get; set; }

Property Value

Type	Description
CacheSyncDependency

Type	Description
Tag[]

Value

The actual object provided by the client application.

Declaration

public virtual object Value { get; set; }

Property Value

Type	Description
System.Object

Remarks

This value must be serializable, otherwise System.ArgumentException is thrown when you will try to add or insert the CacheItem.

Version

Get or Set the cache item version

Declaration

public CacheItemVersion Version { get; set; }

Property Value

Type	Description
CacheItemVersion

Methods

Clone()

Creates a shallow copy of CacheItem

Declaration

public object Clone()

Returns

Type	Description
System.Object

SetCacheDataNotification(CacheDataNotificationCallback, EventType)

Declaration

public void SetCacheDataNotification(CacheDataNotificationCallback callback, EventType eventType)

Parameters

Type	Name	Description
CacheDataNotificationCallback	callback	Callback to be raised when an item is updated or removed
Alachisoft.NCache.Runtime.Events.EventType	eventType	Alachisoft.NCache.Runtime.Events.EventType the callback is registered against

SetCacheDataNotification(CacheDataNotificationCallback, EventType, EventDataFilter)

You can use this to notify applications when their objects are updated or removed in the cache. Callbacks can be registered against Alachisoft.NCache.Runtime.Events.EventType for the key the items is inserted to. To register different Alachisoft.NCache.Runtime.Events.EventDataFilter for different Alachisoft.NCache.Runtime.Events.EventType, you can call this function mutiple times with a different Alachisoft.NCache.Runtime.Events.EventType. Callback are overriden for the same Alachisoft.NCache.Runtime.Events.EventType if called again. Alachisoft.NCache.Runtime.Events.EventType.ItemAdded is not supported yet.

Declaration

public void SetCacheDataNotification(CacheDataNotificationCallback callback, EventType eventType, EventDataFilter datafilter)

Parameters

Type	Name	Description
CacheDataNotificationCallback	callback	Callback to be raised when an item is updated or removed
Alachisoft.NCache.Runtime.Events.EventType	eventType	Alachisoft.NCache.Runtime.Events.EventType the callback is registered against
Alachisoft.NCache.Runtime.Events.EventDataFilter	datafilter	Alachisoft.NCache.Runtime.Events.EventDataFilter for every Alachisoft.NCache.Runtime.Events.EventType registered against