VB.NET

Add a Related File to an HTML Email

Demonstrates the Chilkat Email.AddRelatedFile method, which adds the contents of a local file as a related MIME resource and returns the generated Content-ID. The returned value is the bare Content-ID — no angle brackets and no cid: prefix — so if it returns CID-123@example, the HTML reference is cid:CID-123@example. Because the Content-ID is generated by the call, this example adds the image first, then builds the HTML body in a StringBuilder — using a placeholder in the <img> tag that is replaced with the returned Content-ID — and passes the result to SetHtmlBody.

Background: To embed an image so it displays inside an HTML email (rather than being downloaded from a web server), you add it as a "related" part and reference it from the HTML with a cid: URL that matches the part's Content-ID. Since Chilkat assigns that ID when you add the file, the natural order is: add the related file, capture the returned ID, then build the <img src="cid:..."> reference from it. A StringBuilder makes assembling and updating the HTML convenient.

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'  Demonstrates the AddRelatedFile method, which adds a local file as a related MIME
'  resource (such as an image displayed by an HTML body) and returns the generated
'  Content-ID.  The HTML references the item using cid:<Content-ID>.

Dim email As New Chilkat.Email
email.Subject = "Email with a related image"

'  Add the image file as a related item first.  The return value is the bare Content-ID
'  (no angle brackets and no "cid:" prefix).
Dim cid As String = email.AddRelatedFile("qa_data/images/logo.png")
If (email.LastMethodSuccess = False) Then
    Debug.WriteLine(email.LastErrorText)
    Exit Sub
End If


'  Build the HTML body in a StringBuilder, using a placeholder where the image's
'  Content-ID will go.
Dim sbHtml As New Chilkat.StringBuilder
sbHtml.Append("<html><body><img src=""cid:PLACEHOLDER_CID""/></body></html>")

'  Replace the placeholder with the actual Content-ID returned by AddRelatedFile.
Dim numReplaced As Integer = sbHtml.Replace("PLACEHOLDER_CID",cid)

'  Set the HTML body from the StringBuilder result.
email.SetHtmlBody(sbHtml.GetAsString())

Debug.WriteLine("Related Content-ID = " & cid)
Debug.WriteLine("NumRelatedItems = " & email.NumRelatedItems)

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