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ResolveContentType

function ResolveContentType(AContentType: string): string;

Example​

procedure EffectiveType(const Part: TIdMessagePart; var Value: Variant);
begin
  Value := Part.ResolveContentType(Part.ContentType);
end;

Usage​

ResolveContentType returns nonempty input unchanged or supplies context-sensitive MIME defaults for empty input, including multipart/digest children.

Additional Technical Info​

ResolveContentType supplies Indy's default media type only when AContentType is empty.

ConditionResult
Input nonemptyThe exact input, including parameters and whitespace, unchanged
Empty; item belongs to a MIME-encoded owner message; parent is multipart/digestmessage/rfc822
Empty; item belongs to any other MIME contexttext/plain
Empty; detached, wrong collection, no owner message or non-MIME messageEmpty String

Despite a source comment saying the routine extracts text/plain from a parameterized value, the implementation does not parse nonempty input at all. Callers needing a bare media type must parse it separately; do not assume parameters are removed.

The MIME default path depends on the item being in TIdMessageParts whose owner is TIdMessage with Encoding=meMIME. For a nonnegative hidden ParentPart, it indexes the same collection and inspects that parent's first Content-Type header for multipart/digest.

There is no ParentPart bounds check here. A stale index can raise an indexed collection exception. Parent linkage is not exposed by this generated page set, but decoded/native message structures can contain it.

The method does not write ContentType, repair headers or validate the returned token. Complexity is constant except header lookup. Collection/owner mutation during the call is unsupported.

The source-reviewed example passes the stored header and accepts that an already nonempty parameterized value remains parameterized. It was not executed.

External references

Created 2026-07-15