Hi,

I've just found ClearPost() - it clears all multipart and postdata variables, but content header must be cleared separately.

Working example:

#include <Core/Core.h>

using namespace Upp;

CONSOLE_APP_MAIN
{
	StdLogSetup(LOG_FILE | LOG_CERR | LOG_TIMESTAMP);

	HttpRequest hr("http://posttestserver.com/post.php");
	hr.Trace();
	hr.KeepAlive();
	
	hr.ContentType(Null).ClearPost().New();
	hr.Part("field1", "Lorem ipsum dolor sit amet, consectetur adipiscing elit");
	hr.Part("field2", "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua");
	RLOG(hr.Execute());
	
	hr.ContentType(Null).ClearPost().New();
	hr.Post("field1", "Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat");
	RLOG(hr.Execute());

	hr.ContentType(Null).ClearPost().New();
	hr.Part("field1", "Lorem ipsum dolor sit amet, consectetur adipiscing elit");
	hr.Part("field2", "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua");
	RLOG(hr.Execute());
}