(Delphi DLL) The MIME Content-Type Header Field

Explains the ContentType property and the Content-Type header field including the various attributes that may be included.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Mime;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
mime: HCkMime;

begin
// Every part in a MIME messsage should include a Content-Type header field.
// The Content-Type indicates the type of content contained in the MIME part.
// For example: text/plain, image/jpeg, application/pdf, application/json, multipart/mixed, etc.

// Multipart content types are those where the MIME part's body is composed of N inner MIME messages,
// separated by a boundary string.
// This is how MIME gets a nested, tree-like structure.  The most common multipart MIME types
// are (for email related MIME) multipart/mixed, multipart/alternative, and multipart/related,
// and for HTTP related MIME, it is multipart/form-data.

mime := CkMime_Create();

// The Content-Type header field can be set or modified in two ways.
// 1) By setting the ContentType, Micalg, Name, Charset, Boundary, or Protocol properties.
//    Setting the ContentType property sets the primary value (such as "text/plain") of the header field.
//    Each of the other properties listed above will replace or add a particular attribute value.

// 2) By setting the entire contents of the ContentType header with the SetHeaderField method.
//    This updates each of the Content-Type related properties.

// For example:
CkMime_putContentType(mime,'text/plain');
CkMime_putCharset(mime,'utf-8');

// The Content-Type header field contains this:
//     Content-Type: text/plain; charset=utf-8
Memo1.Lines.Add(CkMime__getEntireHead(mime));
Memo1.Lines.Add('-');

CkMime_SetHeaderField(mime,'Content-Type','image/jpeg; name="kitty.jpg"');
// The Content-Type header field now contains this:
//     Content-Type: image/jpeg; name="kitty.jpg"
Memo1.Lines.Add(CkMime__getEntireHead(mime));
Memo1.Lines.Add('-');

// Notice how the properties have been updated:
Memo1.Lines.Add('ContentType property: ' + CkMime__contentType(mime));
Memo1.Lines.Add('Charset property: ' + CkMime__charset(mime));
Memo1.Lines.Add('Name property: ' + CkMime__name(mime));
Memo1.Lines.Add('-');

// To change a particular attribute value, set the property.
CkMime_putName(mime,'doggy.jpg');
Memo1.Lines.Add(CkMime__getEntireHead(mime));
Memo1.Lines.Add('-');

// To remove an attribute value from the Content-Type header,
// set the property to an empty string.
CkMime_putName(mime,'');
Memo1.Lines.Add(CkMime__getEntireHead(mime));
Memo1.Lines.Add('-');

CkMime_Dispose(mime);

end;