MHT文件本质上是MIME。因此，可以使用Chilkat.Mime或完全免费的System.Net.Mime组件来访问其内部结构。例如，如果MHT包含图像，则可以用输出HTML中的base64字符串替换它们。

Imports HtmlAgilityPack

Imports Fizzler.Systems.HtmlAgilityPack

Imports Chilkat

Public Function ConvertMhtToHtml(ByVal mhtFile As String) As String

Dim chilkatWholeMime As New Chilkat.Mime

'Load mime'

chilkatWholeMime.LoadMimeFile(mhtFile)

'Get html string, which is 1-st part of mime'

Dim html As String = chilkatWholeMime.GetPart(0).GetBodyDecoded

'Create collection for storing url of images and theirs base64 representations'

Dim allImages As New Specialized.NameValueCollection

'Iterate through mime parts'

For i = 1 To chilkatWholeMime.NumParts - 1

Dim m As Chilkat.Mime = chilkatWholeMime.GetPart(i)

'See if it is image'

If m.IsImage AndAlso m.Encoding = "base64" Then

allImages.Add(m.GetHeaderField("Content-Location"), "data:" + m.ContentType + ";base64," + m.GetBodyEncoded)

End If : m.Dispose()

Next : chilkatWholeMime.Dispose()

'Now it is time to replace the source attribute of all images in HTML with dataURI'

Dim htmlDoc As New HtmlDocument : htmlDoc.LoadHtml(html) : Dim docNode As HtmlNode = htmlDoc.DocumentNode

For i = 0 To allImages.Count - 1

'Select all images, whose src attribute is equal to saved URL'

Dim keyURL As String = allImages.GetKey(i) 'Saved url from MHT'

Dim elementsWithPics() As HtmlNode = docNode.QuerySelectorAll("img[src='" + keyURL + "']").ToArray

Dim imgsrc As String = allImages.GetValues(i)(0) 'dataURI as base64 string'

For j = 0 To elementsWithPics.Length - 1

elementsWithPics(j).SetAttributeValue("src", imgsrc)

Next

'Select all elements, whose style attribute contains saved URL'

elementsWithPics = docNode.QuerySelectorAll("[style~='" + keyURL + "']").ToArray

For j = 0 To elementsWithPics.Length - 1

'Get and modify style'

Dim modStyle As String = Strings.Replace(elementsWithPics(j).GetAttributeValue("style", String.Empty), keyURL, imgsrc, 1, 1, 1)

elementsWithPics(j).SetAttributeValue("style", modStyle)

Next : Erase elementsWithPics

Next

'Get final html'

Dim tw As New StringWriter()

htmlDoc.Save(tw) : html = tw.ToString : tw.Close() : tw.Dispose()

Return html

End Function