The following is sample code from AsdkPoly::dxfOutFields():
Acad::ErrorStatus
AsdkPoly::dxfOutFields(AcDbDxfFiler* filer) const
{
assertReadEnabled();
Acad::ErrorStatus es;
if ((es = AcDbCurve::dxfOutFields(filer))
!= Acad::eOk)
{
return es;
}
filer->writeItem(AcDb::kDxfSubclass, "AsdkPoly");
// Object Version
//
Adesk::Int16 version = VERSION;
filer->writeInt16(AcDb::kDxfInt16, version);
filer->writePoint2d(AcDb::kDxfXCoord, mCenter);
filer->writePoint2d(AcDb::kDxfXCoord + 1, mStartPoint);
filer->writeInt32(AcDb::kDxfInt32, mNumSides);
// Always use max precision when writing out the normal.
filer->writeVector3d(AcDb::kDxfNormalX, mPlaneNormal,16);
filer->writeString(AcDb::kDxfText, mpName);
filer->writeItem(AcDb::kDxfHardPointerId, mTextStyle);
filer->writeDouble(AcDb::kDxfReal, mElevation);
return filer->filerStatus();
}