如何从一个LINQ查询表达式中的多个表映射IQueriable?

 private IQueryable<HHDrawingNumber> GetDrawingNumbers()
    {
        var drawingNumbers = from dn in _unitOfWork.DrawingNumbers.Get()
            join ld in _unitOfWork.CfgLocDrawing.Get() on dn.LocDrawingNum equals ld.DrawingsId
            join ar in _unitOfWork.AssetReg.Get() on dn.AssetId equals ar.LastData
            select new HHDrawingNumber
            {
                TagNumber = dn.TagNumber ?? string.Empty,
                DrawingsId = ld.DrawingsId,
                DrawingsCode = ld.DrawingsCode ?? string.Empty,
                DrawingsDescription = ld.DrawingsDescription ?? string.Empty
            };
        return drawingNumbers;
    }