B4X

Get a MIME Header Field Value

Demonstrates the Chilkat Mime.GetHeaderField method, which returns the value of the first header field whose name matches case-insensitively. The only argument is the field name; it returns null when no matching field exists.

Note: The file path is relative to the application's current working directory. Absolute paths may also be used. Supply the path to your own file.

Background: This is the everyday way to read a header value — the Subject, a Message-ID, a custom X- header. Because a missing field returns null, the returned value is assigned to a variable and checked rather than used directly, so an absent header is handled cleanly instead of surfacing as an error later. Only the first matching occurrence is returned; iterate by index to see duplicates.

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Dim success As Boolean = False

Dim mime As ChilkatMime
mime.Initialize
success = mime.LoadMimeFile("qa_data/message.eml")
If success = False Then
    Log(mime.LastErrorText)
    Return
End If


'  Return the value of the first header field with a matching (case-insensitive) name.
'  GetHeaderField returns null when no matching field exists, so assign it to a string variable
'  and check for success.
Dim subject As String = mime.GetHeaderField("Subject")
If mime.LastMethodSuccess = False Then
    Log(mime.LastErrorText)
    Return
End If

Log("Subject: " & subject)