实体的句柄类型，实体的句柄在dwg图中可以唯一标识一个实体，并且它能随图保存。由句柄就能得到实体的ID(调用McDbDatabase::getAcDbObjectId()函数)，就能得到实体对象
class McDbHandle;
McDbHandle.h
例如:由实体名柄得到实体ID的例程代码
McDbHandle handle(_T("1A388"));
McDbObjectId retId;
acdbHostApplicationServices()->workingDatabase()->getAcDbObjectId(retId,false,handle);由实体ID得到实体名柄的例程代码
McDbObjectId entId = pickedEntities[0];
McDbObjectPointer<McDbEntity> spEnt(entId,McDb::kForRead);
if(spEnt.openStatus() == Mcad::eOk)
{
McDbHandle handle;
spEnt->getAcDbHandle(handle);
TCHAR szHandle[256];
handle.getIntoAsciiBuffer(szHandle);
}