VB.NET

Get the Content-ID of a Related Item

Demonstrates the Chilkat Email.GetRelatedContentID method, which returns the Content-ID of a related item (typically an image or style sheet embedded within an HTML email). The index is zero-based. This example loads an image from a file into a BinData object, adds it as a related item with AddRelatedBd (capturing the generated Content-ID and referencing it from the HTML), then reads that Content-ID back.

Background: The Content-ID is the anchor that ties an inline resource to the HTML that displays it: the body references cid: plus the ID, and the matching related part carries that same Content-ID. Because an image is binary, it is loaded into a BinData object (here from a file) and added with AddRelatedBd. Reading the Content-ID back lets a program verify or rewrite those links — for example when relocating embedded images or converting a message for display outside a mail client.

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Dim success As Boolean = False

'  Demonstrates the GetRelatedContentID method, which returns the Content-ID of a related
'  item.  Related items are typically images and style sheets embedded within HTML emails.
'  The index is zero-based.

Dim email As New Chilkat.Email
email.Subject = "GetRelatedContentID example"

'  Load the image data from a file into a BinData object.
Dim bdImage As New Chilkat.BinData
success = bdImage.LoadFile("qa_data/images/logo.png")
If (success = False) Then
    Debug.WriteLine(bdImage.LastErrorText)
    Exit Sub
End If


'  Add the image as a related item from the BinData; capture its generated Content-ID.
Dim cid As String = email.AddRelatedBd("logo.png",bdImage)
If (email.LastMethodSuccess = False) Then
    Debug.WriteLine(email.LastErrorText)
    Exit Sub
End If


'  Reference the related item in the HTML body by its Content-ID.
Dim sbHtml As New Chilkat.StringBuilder
sbHtml.Append("<html><body><img src=""cid:PLACEHOLDER_CID""/></body></html>")
Dim numReplaced As Integer = sbHtml.Replace("PLACEHOLDER_CID",cid)
email.SetHtmlBody(sbHtml.GetAsString())

'  Read the Content-ID of the first related item (index 0).
Dim cid0 As String = email.GetRelatedContentID(0)
Debug.WriteLine("Related item 0 Content-ID: " & cid0)

'  Note: The path "qa_data/images/logo.png" is a relative local filesystem path,
'  relative to the current working directory of the running application.