Mht VB.NET Reference Documentation

Mht

Chilkat MHT can generate email objects from HTML files and URLs, and convert HTML to MHT or EML files.

Object Creation

Dim obj As New Chilkat.Mht()

Properties

AbortCurrent As Boolean

Introduced in version 9.5.0.58

When set to True, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to False when the next method is called. When the abort occurs, this property is reset to False. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)

BaseUrl As String

When processing an HTML file or string (not a website URL), this defines the base URL to be used when converting relative HREFs to absolute HREFs.

ConnectTimeout As Integer

The amount of time in seconds to wait before timing out when connecting to an HTTP server. The default value is 10 seconds.

DebugHtmlAfter As String

A filename to save the result HTML when converting a URL, file, or HTML string. If problems are experienced, the before/after HTML can be analyzed to help determine the cause.

DebugHtmlBefore As String

A filename to save the input HTML when converting a URL, file, or HTML string. If problems are experienced, the before/after HTML can be analyzed to help determine the cause.

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:

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

DebugTagCleaning As Boolean

When True causes the Mht class to be much more verbose in its logging. The default is False.

EmbedImages As Boolean

Controls whether images are embedded in the MHT/EML, or whether the IMG SRC attributes are left as external URL references. If false, the IMG SRC tags are converted to absolute URLs (if necessary) and the images are not embedded within the MHT/EML.

EmbedLocalOnly As Boolean

If True, only images found on the local filesystem (i.e. links to files) will be embedded within the MHT.

FetchFromCache As Boolean

If True, page parts such as images, style sheets, etc. will be fetched from the disk cache if possible. The disk cache root may be defined by calling AddCacheRoot. The default value is False.

HeartbeatMs As Integer

The time interval, in milliseconds, between AbortCheck event callbacks. The heartbeat/AbortCheck provides a means for an application to abort any MHT method before completion.

The default value is 0, which means that no AbortCheck events will be fired.

IgnoreMustRevalidate As Boolean

Some HTTP responses contain a "Cache-Control: must-revalidate" header. If this is present, the server is requesting that the client always issue a revalidate HTTP request instead of serving the page directly from cache. If IgnoreMustRevalidate is set to True, then Chilkat MHT will serve the page directly from cache without revalidating until the page is no longer fresh. (assuming that FetchFromCache is set to True)

The default value of this property is False.

IgnoreNoCache As Boolean

Some HTTP responses contain headers of various types that indicate that the page should not be cached. Chilkat MHT will adhere to this unless this property is set to True.

The default value of this property is False.

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 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.

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 As Boolean

Introduced in version 9.5.0.52

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.

NoScripts As Boolean

Only applies when creating MHT files. Scripts are always removed when creating EML or emails from HTML. If set to True, then all scripts are removed, if set to False (the default) then scripts are not removed.

NtlmAuth As Boolean

Setting this property to True causes the MHT component to use NTLM authentication (also known as IWA -- or Integrated Windows Authentication) when authentication with an HTTP server.

The default value of this property is False.

NumCacheLevels As Integer

The number of directory levels to be used under each cache root. The default is 0, meaning that each cached item is stored in a cache root directory. A value of 1 causes each cached page to be stored in one of 255 subdirectories named "0","1", "2", ..."255" under a cache root. A value of 2 causes two levels of subdirectories ("0..255/0..255") under each cache root. The MHT control automatically creates subdirectories as needed. The reason for mutliple levels is to alleviate problems that may arise when huge numbers of files are stored in a single directory. For example, Windows Explorer does not behave well when trying to display the contents of directories with thousands of files.

NumCacheRoots As Integer (ReadOnly)

The number of cache roots to be used for the disk cache. This allows the disk cache spread out over multiple disk drives. Each cache root is a string indicating the drive letter and directory path. For example, "E:\Cache". To create a cache with four roots, call AddCacheRoot once for each directory root.

PreferIpv6 As Boolean

If True, then use IPv6 over IPv4 when both are supported for a particular domain. The default value of this property is False, which will choose IPv4 over IPv6.

PreferMHTScripts As Boolean

This property provides a means for the noscript option to be selected when possible. If PreferMHTScripts = False, then scripts with noscript alternatives are removed and the noscript content is kept. If True (the default), then scripts are preserved and the noscript options are discarded.

Proxy As String

(Optional) A proxy host:port if a proxy is necessary to access the Internet. The proxy string should be formatted as "hostname:port", such as "www.chilkatsoft.com:100".

ProxyLogin As String

If an HTTP proxy is used and it requires authentication, this property specifies the HTTP proxy login.

ProxyPassword As String

If an HTTP proxy is used and it requires authentication, this property specifies the HTTP proxy password.

ReadTimeout As Integer

The amount of time in seconds to wait before timing out when reading from an HTTP server. The ReadTimeout is the amount of time that needs to elapse while no additional data is forthcoming. During a long data transfer, if the data stream halts for more than this amount, it will timeout. Otherwise, there is no limit on the length of time for the entire data transfer.

The default value is 20 seconds.

RequireSslCertVerify As Boolean

If True, then the HTTP client will verify the server's SSL certificate. The certificate is expired, or if the cert's signature is invalid, the connection is not allowed. The default value of this property is False.

SocksHostname As String

The SOCKS4/SOCKS5 hostname or IPv4 address (in dotted decimal notation). This property is only used if the SocksVersion property is set to 4 or 5).

SocksPassword As String

The SOCKS5 password (if required). The SOCKS4 protocol does not include the use of a password, so this does not apply to SOCKS4.

SocksPort As Integer

The SOCKS4/SOCKS5 proxy port. The default value is 1080. This property only applies if a SOCKS proxy is used (if the SocksVersion property is set to 4 or 5).

SocksUsername As String

The SOCKS4/SOCKS5 proxy username. This property is only used if the SocksVersion property is set to 4 or 5).

SocksVersion As Integer

SocksVersion May be set to one of the following integer values:

0 - No SOCKS proxy is used. This is the default.
4 - Connect via a SOCKS4 proxy.
5 - Connect via a SOCKS5 proxy.

UnpackDirect As Boolean

Introduced in version 9.5.0.47

If True, then the UnpackMHT and UnpackMHTString methods will unpack the MHT directly with no transformations. Normally, the related parts are unpacked to a "parts" sub-directory, and the unpacked HTML is edited to update references to point to the unpacked image and script files. When unpacking direct, the HTML is not edited, and the related parts are unpacked to sub-directories rooted in the directory where HTML file is created (i.e. the unpack directory). When unpacking direct, the "partsSubDir" argument of the UnpackMHT* methods is unused.

Note: It is only possible to directly unpack MHT files where the Content-Location headers DO NOT contain URLs. The MHT must be such that the Content-Location headers of the related items contain relative paths.

Note: The default value of this property is False.

UnpackUseRelPaths As Boolean

Controls whether absolute or relative paths are used when referencing images in the unpacked HTML. The default value is True indicating that relative paths will be used. To use absolute paths, set this property value equal to False.

UpdateCache As Boolean

Controls whether the cache is automatically updated with the responses from HTTP GET requests. If True, the disk cache is updated, if False (the default), the cache is not updated.

UseCids As Boolean

Controls whether CID URLs are used for embedded references when generating MHT or EML documents. If UseCids is False, then URLs are left unchanged and the embedded items will contain "content-location" headers that match the URLs in the HTML. If True, CIDs are generated and the URLs within the HTML are replaced with "CID:" links.

The default value of this property is True.

UseFilename As Boolean

If True, a "filename" attribute is added to each Content-Disposition MIME header field for each embedded item (image, style sheet, etc.). If False, then no filename attribute is added.

The default value of this property is True.

UseIEProxy As Boolean

If True, the proxy host/port used by Internet Explorer will also be used by Chilkat MHT.

UseInline As Boolean

If True, an "inline" attribute is added to each Content-Disposition MIME header field for each embedded item (image, style sheet, etc.). If False, then no inline attribute is added.

The default value of this property is True.

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 As String (ReadOnly)

Version of the component/library, such as "9.4.1.42"

WebSiteLogin As String

(Optional) Specifies the login if a a Web page is accessed that requires a login

WebSiteLoginDomain As String

The optional domain name to be used with NTLM / Kerberos / Negotiate authentication.

WebSitePassword As String

Optional) Specifies the password if a a Web page is accessed that requires a login and password

Methods

Sub AddCacheRoot(ByVal dir As String)

If disk caching is used, this 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".

(VB.NET) Download Web Page to MHT with w/ Disk Cache

(PowerShell) Download Web Page to MHT with w/ Disk Cache

Sub AddCustomHeader(ByVal name As String, ByVal value As String)

Adds a custom HTTP header to all HTTP requests sent by the MHT component. To add multiple header fields, call this method once for each custom header.

Sub AddExternalStyleSheet(ByVal url As String)

(This method rarely needs to be called.) Includes an additional style sheet that would not normally be included with the HTML. This method is provided for cases when style sheet names are constructed and dynamically included in Javascript such that MHT .NET cannot know beforehand what stylesheet to embed. MHT .NET by default downloads and embeds all stylesheets externally referenced by the HTML

Sub ClearCustomHeaders()

Removes all custom headers that may have accumulated from previous calls to AddCustomHeader.

Sub ExcludeImagesMatching(ByVal pattern As String)

(This method rarely needs to be called.) Tells Chilkat MHT .NET to not embed any images whose URL matches a pattern. Sometimes images can be referenced within style sheets and not actually used when rendering the page. In cases like those, the image will appear as an attachment in the HTML email. This feature allows you to explicitly remove those images from the email so no attachments appear.

Function GetAndSaveEML(ByVal url_or_htmlFilepath As String, ByVal emlPath As String) As Boolean

Creates an EML file from a web page or HTML file. All external images and style sheets are downloaded and embedded in the EML file.

Returns True for success, False for failure.

Function GetAndSaveEMLAsync(ByVal url_or_htmlFilepath As String, ByVal emlPath As String) As Task

Creates an asynchronous task to call the GetAndSaveEML 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function GetAndSaveMHT(ByVal url_or_htmlFilepath As String, ByVal mhtPath As String) As Boolean

Creates an MHT file from a web page or local HTML file. All external images, scripts, and style sheets are downloaded and embedded in the MHT file.

Returns True for success, False for failure.

Function GetAndSaveMHTAsync(ByVal url_or_htmlFilepath As String, ByVal mhtPath As String) As Task

Creates an asynchronous task to call the GetAndSaveMHT 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function GetAndZipEML(ByVal url_or_htmlFilepath As String, ByVal zipEntryFilename As String, ByVal zipFilename As String) As Boolean

Creates an EML file from a web page or HTML file, compresses, and appends to a new or existing Zip file. All external images and style sheets are downloaded and embedded in the EML.

Returns True for success, False for failure.

Function GetAndZipEMLAsync(ByVal url_or_htmlFilepath As String, ByVal zipEntryFilename As String, ByVal zipFilename As String) As Task

Creates an asynchronous task to call the GetAndZipEML 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function GetAndZipMHT(ByVal url_or_htmlFilepath As String, ByVal zipEntryFilename As String, ByVal zipFilename As String) As Boolean

Creates an MHT file from a web page or HTML file, compresses, and appends to a new or existing Zip file. All external images and style sheets are downloaded and embedded in the MHT.

Returns True for success, False for failure.

Function GetAndZipMHTAsync(ByVal url_or_htmlFilepath As String, ByVal zipEntryFilename As String, ByVal zipFilename As String) As Task

Creates an asynchronous task to call the GetAndZipMHT 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function GetCacheRoot(ByVal index As Integer) As String

Returns the Nth cache root (indexing begins at 0). Cache roots are set by calling AddCacheRoot one or more times.

Returns Nothing on failure

Function GetEML(ByVal url_or_htmlFilepath As String) As String

Creates EML from a web page or HTML file, and returns the EML (MIME) message data as a string.

Returns Nothing on failure

Function GetEMLAsync(ByVal url_or_htmlFilepath As String) As Task

Creates an asynchronous task to call the GetEML 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function GetMHT(ByVal url_or_htmlFilepath As String) As String

Creates MHT from a web page or local HTML file, and returns the MHT (MIME) message data as a string

Returns Nothing on failure

Function GetMHTAsync(ByVal url_or_htmlFilepath As String) As Task

Creates an asynchronous task to call the GetMHT 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function HtmlToEML(ByVal htmlText As String) As String

Creates an in-memory EML string from an in-memory HTML string. All external images and style sheets are downloaded and embedded in the EML string that is returned.

Returns Nothing on failure

Function HtmlToEMLAsync(ByVal htmlText As String) As Task

Creates an asynchronous task to call the HtmlToEML 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function HtmlToEMLFile(ByVal html As String, ByVal emlFilename As String) As Boolean

Creates an EML file from an in-memory HTML string. All external images and style sheets are downloaded and embedded in the EML file.

Returns True for success, False for failure.

Function HtmlToEMLFileAsync(ByVal html As String, ByVal emlFilename As String) As Task

Creates an asynchronous task to call the HtmlToEMLFile 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function HtmlToMHT(ByVal htmlText As String) As String

Creates an in-memory MHT web archive from an in-memory HTML string. All external images and style sheets are downloaded and embedded in the MHT string.

Returns Nothing on failure

Function HtmlToMHTAsync(ByVal htmlText As String) As Task

Creates an asynchronous task to call the HtmlToMHT 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function HtmlToMHTFile(ByVal html As String, ByVal mhtFilename As String) As Boolean

Creates an MHT file from an in-memory HTML string. All external images and style sheets are downloaded and embedded in the MHT file.

Returns True for success, False for failure.

Function HtmlToMHTFileAsync(ByVal html As String, ByVal mhtFilename As String) As Task

Creates an asynchronous task to call the HtmlToMHTFile 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.

(VB.NET) How to Run an Asynchronous Task

(PowerShell) How to Run an Asynchronous Task

Function IsUnlocked() As Boolean

Returns True if the MHT component is unlocked.

Sub RemoveCustomHeader(ByVal name As String)

Removes a custom header by header field name.

Sub RestoreDefaults()

Restores the default property settings.

Function SaveLastError(ByVal path As String) As Boolean

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns True for success, False for failure.

Function UnlockComponent(ByVal unlockCode As String) As Boolean

Unlocks the component allowing for the full functionality to be used. Returns True if the unlock code is valid.

Returns True for success, False for failure.

Diagnosing UnlockComponent Problems

UnlockComponent LastErrorText shows exact string passed to it.

Verify UnlockComponent Success w/ Permanent Unlock Code

LastErrorText Standard Information

Function UnpackMHT(ByVal mhtFilename As String, ByVal unpackDir As String, ByVal htmlFilename As String, ByVal partsSubDir As String) As Boolean

Unpacks the contents of a MHT file. The destination directory is specified by unpackDir. The name of the HTML file created is specified by htmlFilename, and supporting files (images, javascripts, etc.) are created in partsSubDir, which is automatically created if it does not already exist.

Returns True for success, False for failure.

Function UnpackMHTString(ByVal mhtString As String, ByVal unpackDir As String, ByVal htmlFilename As String, ByVal partsSubDir As String) As Boolean

Same as UnpackMHT, except the MHT is passed in as an in-memory string.

Returns True for success, False for failure.

Events

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 mht As Chilkat.Mht

Private Sub mht_OnAbortCheck(sender As Object, args As Chilkat.AbortCheckEventArgs) Handles mht.OnAbortCheck

    ...

End Sub

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 mht As Chilkat.Mht

Private Sub mht_OnProgressInfo(sender As Object, args As Chilkat.ProgressInfoEventArgs) Handles mht.OnProgressInfo

    ...

End Sub

Event OnTaskCompleted

Called in the background thread when an asynchronous task completes.

VB.NET TaskCompleted Event Callback Example

Args are passed using Chilkat.TaskCompletedEventArgs

Event callback implementation:

Dim WithEvents mht As Chilkat.Mht

Private Sub mht_OnTaskCompleted(sender As Object, args As Chilkat.TaskCompletedEventArgs) Handles mht.OnTaskCompleted

    ...

End Sub