B4X

Enumerate MIME Header Field Names

Demonstrates the Chilkat Mime.GetHeaderFieldName method, which returns the name of the header-field occurrence at a zero-based index. The only argument is the index; use NumHeaderFields for the count. Original order and casing are preserved.

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: When you need to walk all the headers — to display them, copy them, or handle duplicates that GetHeaderField would hide — index-based access is the way. NumHeaderFields bounds the loop, and this returns each field's name in its original order and casing, which matters when the exact header sequence is significant.

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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


'  Iterate the header fields by index.  NumHeaderFields gives the count; GetHeaderFieldName and
'  GetHeaderFieldValue return the name and value at each zero-based index.  Original order and
'  casing are preserved.
Dim n As Int = mime.NumHeaderFields
Log("Header fields: " & n)
Dim i As Int
For i = 0 To n - 1
    Dim fieldName As String = mime.GetHeaderFieldName(i)
    If mime.LastMethodSuccess = False Then
        Log(mime.LastErrorText)
        Return
    End If

    Log(fieldName)
Next