Cache VB.NET Reference Documentation

Cache

Current Version: 10.0.0

Requires Chilkat Bundle License

Object Creation

Dim obj As New Chilkat.Cache()

Properties

DebugLogFilePath

DebugLogFilePath As String

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
there is an internal problem (bug) in the Chilkat code that causes the hang.

More Information and Examples

Example showing how to use DebugLogFilePath.

LastErrorHtml

LastErrorHtml As String (ReadOnly)

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

LastErrorText

LastErrorText As String (ReadOnly)

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

More Information and Examples

Concept of LastErrorText LastErrorText Standard Information

LastErrorXml

LastErrorXml As String (ReadOnly)

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

LastEtagFetched

LastEtagFetched As String (ReadOnly)

The ETag of the last item fetched from cache.

LastExpirationFetchedStr

LastExpirationFetchedStr As String (ReadOnly)

Expiration date/time of the last item fetched from cache in RFC822 string format.

LastHitExpired

LastHitExpired As Boolean (ReadOnly)

True if the LastExpirationFetched is before the current date/time. Otherwise False.

LastKeyFetched

LastKeyFetched As String (ReadOnly)

The key of the last item fetched from cache. (For web pages, the key is typically the canonicalized URL. Otherwise, the key is a unique identifer used to access the cached item.)

LastMethodSuccess

LastMethodSuccess As Boolean

Indicate whether the last method call succeeded or failed. A value of True indicates success, a value of False indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

Any method that returns a string.
Any method returning a Chilkat object, binary bytes, or a date/time.
Any method returning a standard boolean status value where success = True and failure = False.
Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to True. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

Level

Level As Integer

The number of directory levels in the cache. Possible values are:

0: All cache files are in a single directory (the cache root).

1: Cache files are located in 256 sub-directories numbered 0 .. 255 directly under the cache root.

2: There are two levels of sub-directories under the cache root. The 1st level has 256 sub-directories numbered 0 .. 255 directly under the cache root. The 2nd level allows for up to 256 sub-directories (0..255) under each level-1 directory. Cache files are stored in the leaf directories.

NumRoots

NumRoots As Integer (ReadOnly)

The number of root directories composing the cache. A typical multi-root cache would place each root on a separate hard drive.

VerboseLogging

VerboseLogging As Boolean

If set to True, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

Version

Version As String (ReadOnly)

Version of the component/library, such as "9.5.0.94"

More Information and Examples

How to get the Chilkat version at runtime.

Methods

AddRoot

Sub AddRoot(ByVal path As String)

Must be called once for each cache root. For example, if the cache is spread across D:\cacheRoot, E:\cacheRoot, and F:\cacheRoot, an application would setup the cache object by calling AddRoot three times -- once with "D:\cacheRoot", once with "E:\cacheRoot", and once with "F:\cacheRoot".

More Information and Examples

Large Persistent Hash Table Stored on Filesystem

DeleteAll

Function DeleteAll() As Integer

Deletes all items in the cache. This method completely clears the cache. All files in the cache are deleted. (If the cache is multi-level, existing sub-directories are not deleted.)

Returns the number of items (i.e. cache files) deleted.

DeleteAllExpired

Function DeleteAllExpired() As Integer

Deletes all expired items from the cache.

Returns the number of items (i.e. cache files) deleted.

DeleteFromCache

Function DeleteFromCache(ByVal key As String) As Boolean

Deletes a single item from the disk cache. Returns False if the item exists in cache but could not be deleted. Otherwise returns True.

Returns True for success, False for failure.

DeleteOlderDt

Function DeleteOlderDt(ByVal dateTime As CkDateTime) As Integer

The same as DeleteOlder, except the dateTime is passed as a CkDateTime.

DeleteOlderStr

Function DeleteOlderStr(ByVal dateTimeStr As String) As Integer

The same as DeleteOlder, except the dateTimeStr is passed as a date/time in RFC822 format.

FetchBd

Function FetchBd(ByVal key As String, ByVal bd As BinData) As Boolean

Introduced in version 9.5.0.91

Fetches an item from cache and returns in bd.

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns True for success, False for failure.

FetchFromCache

Function FetchFromCache(ByVal key As String) As Byte()

Fetches an item from cache.

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns an empty byte array on failure

More Information and Examples

Facebook Download all Photos to Local Files

FetchSb

Function FetchSb(ByVal key As String, ByVal sb As StringBuilder) As Boolean

Introduced in version 9.5.0.91

Fetches a text item from the cache and returns in sb.

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns True for success, False for failure.

FetchText

Function FetchText(ByVal key As String) As String

Fetches a text item from the cache and returns it's text content.

The key may be any length and may include any characters. It should uniquely identify the cached item. (No two items in the cache should have the same key.)

Returns Nothing on failure

More Information and Examples

Large Persistent Hash Table Stored on Filesystem

GetEtag

Function GetEtag(ByVal key As String) As String

Returns the eTag for an item in the cache.

Returns Nothing on failure

GetExpirationDt

Function GetExpirationDt(ByVal key As String) As CkDateTime

Returns the expiration date/time for an item in the cache as a CkDateTime object.

Returns Nothing on failure

GetExpirationStr

Function GetExpirationStr(ByVal url As String) As String

Returns the expiration date/time for an item in the cache in RFC822 string format.

Returns Nothing on failure

GetFilename

Function GetFilename(ByVal key As String) As String

Returns the absolute file path of the cache file associated with the key.

Returns Nothing on failure

GetRoot

Function GetRoot(ByVal index As Integer) As String

Returns the directory path of the Nth cache root. (Indexing begins at 0.)

Returns Nothing on failure

IsCached

Function IsCached(ByVal key As String) As Boolean

Returns True if the item is found in the cache, otherwise returns False.

SaveTextDt

Function SaveTextDt(ByVal key As String, ByVal expireDateTime As CkDateTime, ByVal eTag As String, ByVal itemTextData As String) As Boolean

The same as SaveText, except the expire date/time is passed as a CkDateTime object.

Returns True for success, False for failure.

SaveTextNoExpire

Function SaveTextNoExpire(ByVal key As String, ByVal eTag As String, ByVal itemTextData As String) As Boolean

Inserts or replaces an text item in the cache with no expiration date/time. The eTag is optional and may be set to a zero-length string. Applications may use it as a place to save additional information about the cached item.

Returns True for success, False for failure.

More Information and Examples

Large Persistent Hash Table Stored on Filesystem

SaveTextStr

Function SaveTextStr(ByVal key As String, ByVal expireDateTime As String, ByVal eTag As String, ByVal itemTextData As String) As Boolean

The same as SaveText, except the expire date/time is passed as a string in RFC822 format.

Returns True for success, False for failure.

SaveToCacheDt

Function SaveToCacheDt(ByVal key As String, ByVal expireDateTime As CkDateTime, ByVal eTag As String, ByVal itemData As Byte()) As Boolean

The same as SaveToCache, except the expire date/time is passed as a CkDateTime object.

Returns True for success, False for failure.

SaveToCacheNoExpire

Function SaveToCacheNoExpire(ByVal key As String, ByVal eTag As String, ByVal itemData As Byte()) As Boolean

Inserts or replaces an item in the cache. The cached item will have no expiration. The eTag is optional and may be set to a zero-length string. Applications may use it as a place to save additional information about the cached item.

Returns True for success, False for failure.

More Information and Examples

Facebook Download all Photos to Local Files

SaveToCacheStr

Function SaveToCacheStr(ByVal key As String, ByVal expireDateTime As String, ByVal eTag As String, ByVal itemData As Byte()) As Boolean

The same as SaveToCache, except the expire date/time is passed in RFC822 string format.

Returns True for success, False for failure.

UpdateExpirationDt

Function UpdateExpirationDt(ByVal key As String, ByVal expireDateTime As CkDateTime) As Boolean

The same as UpdateExpiration, except the expireDateTime is passed as a CkDateTime.

Returns True for success, False for failure.

UpdateExpirationStr

Function UpdateExpirationStr(ByVal key As String, ByVal expireDateTime As String) As Boolean

The same as UpdateExpiration, except the expireDateTime is passed in RFC822 string format.

Returns True for success, False for failure.