Rss VB.NET Reference Documentation

Rss

Current Version: 10.0.0

Represents an RSS document or sub-part of a document such as a channel, image, or item. The RSS API allows one to download, create and modify RSS documents.

Object Creation

Dim obj As New Chilkat.Rss()

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.

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.

NumChannels

NumChannels As Integer (ReadOnly)

The number of channels in the RSS document.

NumItems

NumItems As Integer (ReadOnly)

The number of items in the channel.

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

AddNewChannel

Function AddNewChannel() As Rss

Adds a new channel to the RSS document. Returns the Rss object representing the Channel which can then be edited.

Returns Nothing on failure

AddNewImage

Function AddNewImage() As Rss

Adds a new image to the RSS document. Returns the Rss object representing the image, which can then be edited.

Returns Nothing on failure

AddNewItem

Function AddNewItem() As Rss

Adds a new Item to an Rss channel. Returns the Rss object representing the item which can then be edited.

Returns Nothing on failure

DownloadRss

Function DownloadRss(ByVal url As String) As Boolean

Downloads an RSS document from the Internet and populates the Rss object with the contents.

Returns True for success, False for failure.

More Information and Examples

Example: Read RSS Feed

DownloadRssAsync ⁽¹⁾

Function DownloadRssAsync(ByVal url As String) As Task

Creates an asynchronous task to call the DownloadRss method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.

Returns Nothing on failure

GetAttr

Function GetAttr(ByVal tag As String, ByVal attrName As String) As String

Returns the value of a sub-element attribute. For example, to get the value of the "isPermaLink" attribute of the "guid" sub-element, call item.GetAttr("guid","isPermaLink").

Returns Nothing on failure

GetChannel

Function GetChannel(ByVal index As Integer) As Rss

Returns the Nth channel of an RSS document. Usually there is only 1 channel per document, so the index argument should be set to 0.

Returns Nothing on failure

GetCount

Function GetCount(ByVal tag As String) As Integer

Return the number of sub-elements with a specific tag.

GetDateStr

Function GetDateStr(ByVal tag As String) As String

The same as GetDate, except the date/time is returned in RFC822 string format.

Returns Nothing on failure

GetImage

Function GetImage() As Rss

Return the image associated with the channel.

Returns Nothing on failure

GetInt

Function GetInt(ByVal tag As String) As Integer

Return the value of a numeric sub-element as an integer.

GetItem

Function GetItem(ByVal index As Integer) As Rss

Return the Nth item of a channel as an RSS object.

Returns Nothing on failure

GetString

Function GetString(ByVal tag As String) As String

Return the value of an sub-element as a string.

Returns Nothing on failure

LoadRssFile

Function LoadRssFile(ByVal filePath As String) As Boolean

Load an RSS document from a file.

Returns True for success, False for failure.

LoadRssString

Function LoadRssString(ByVal rssString As String) As Boolean

Loads an RSS feed document from an in-memory string.

Returns True for success, False for failure.

LoadTaskCaller

Function LoadTaskCaller(ByVal task As Task) As Boolean

Introduced in version 9.5.0.80

Loads the caller of the task's async method.

Returns True for success, False for failure.

MGetAttr

Function MGetAttr(ByVal tag As String, ByVal index As Integer, ByVal attrName As String) As String

Get an attribute value for the Nth sub-element having a specific tag. As an example, an RSS item may have several "category" sub-elements. To get the value of the "domain" attribute for the 3rd category, call MGetAttr("category",2,"domain").

Returns Nothing on failure

MGetString

Function MGetString(ByVal tag As String, ByVal index As Integer) As String

Get the value of the Nth occurrence of a sub-element. Indexing begins at 0.

Returns Nothing on failure

MSetAttr

Function MSetAttr(ByVal tag As String, ByVal idx As Integer, ByVal attrName As String, ByVal value As String) As Boolean

Set an attribute on the Nth occurrence of a sub-element.

Returns True for success, False for failure.

MSetString

Function MSetString(ByVal tag As String, ByVal idx As Integer, ByVal value As String) As Boolean

Set the value of the Nth occurrence of a sub-element. Indexing begins at 0.

Returns True for success, False for failure.

NewRss

Sub NewRss()

Clears the RSS document.

Remove

Sub Remove(ByVal tag As String)

Removes a sub-element from the RSS document.

SetAttr

Sub SetAttr(ByVal tag As String, ByVal attrName As String, ByVal value As String)

Sets the value of a sub-element attribute.

SetDateNow

Sub SetDateNow(ByVal tag As String)

Sets the value of a date/time sub-element to the current system date/time.

SetDateStr

Sub SetDateStr(ByVal tag As String, ByVal dateTimeStr As String)

The same as SetDate, except the date/time is passed as an RFC822 string.

SetInt

Sub SetInt(ByVal tag As String, ByVal value As Integer)

Sets the value of an integer sub-element.

SetString

Sub SetString(ByVal tag As String, ByVal value As String)

Sets the value of a sub-element.

ToXmlString

Function ToXmlString() As String

Returns the RSS document as an XML string.

Returns Nothing on failure

Events

AbortCheck

Event OnAbortCheck

Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200.

Args are passed using Chilkat.AbortCheckEventArgs

Event callback implementation:

Dim WithEvents rss As Chilkat.Rss

Private Sub rss_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles rss.OnAbortCheck

    ...

End Sub

PercentDone

Event OnPercentDone

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.

The abort output argument provides a means for aborting the operation. Setting it to True will cause the method to abort and return a failed status (or whatever return value indicates failure).

Args are passed using Chilkat.PercentDoneEventArgs

Event callback implementation:

Dim WithEvents rss As Chilkat.Rss

Private Sub rss_OnPercentDone(sender As Object, args As Chilkat.PercentDoneEventArgs) Handles rss.OnPercentDone

    ...

End Sub

ProgressInfo

Event OnProgressInfo

A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.

Args are passed using Chilkat.ProgressInfoEventArgs

Event callback implementation:

Dim WithEvents rss As Chilkat.Rss

Private Sub rss_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles rss.OnProgressInfo

    ...

End Sub

TaskCompleted

Event OnTaskCompleted

Called in the background thread when an asynchronous task completes.

More Information and Examples

VB.NET TaskCompleted Event Callback Example

Args are passed using Chilkat.TaskCompletedEventArgs

Event callback implementation:

Dim WithEvents rss As Chilkat.Rss

Private Sub rss_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles rss.OnTaskCompleted

    ...

End Sub

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