Linq-C#左连接

var list = (from dr in dt_project.AsEnumerable()
join d1 in list_businessclass on dr.Field<Guid?>("BusinessClass") equals d1.ID into temp0
from tp0 in temp0.DefaultIfEmpty()
join d2 in list_dic_ppmodle on dr.Field<Guid?>("SanctionPPMode") equals d2.ID into temp1
from tp1 in temp1.DefaultIfEmpty()
join d3 in list_dic_ppmodle on dr.Field<Guid?>("RealPPMode") equals d3.ID into temp2
from tp2 in temp2.DefaultIfEmpty()
select new
{
ProjectID = dr.Field<Guid?>("ProjectID"),
ResponsibleUnit = dr.Field<Guid?>("ResponsibleUnit"),
OwnerUnitName = dr.Field<string>("OwnerUnitName"),//,
ProjectName = dr.Field<string>("ProjectName"),
BusinessClass = dr.Field<Guid?>("BusinessClass"),
BusinessClassText = (tp0 == null ? "" : tp0.Title),
//设立
EstablishedTime = dr.Field<DateTime?>("EstablishedTime") == null ? "" : Convert.ToDateTime(dr.Field<DateTime?>("EstablishedTime")).ToString("yyyy-MM-dd"),//立项时间
EstablishReplyCode = dr.Field<string>("EstablishReplyCode"),//立项批复文号
EstablishReplyCodeAttach = dr.Field<string>("EstablishReplyCodeAttach"),//立项批复文号附件
//可研
FeasibilityStudyReplyTime = dr.Field<DateTime?>("FeasibilityStudyReplyTime") == null ? "" : Convert.ToDateTime(dr.Field<DateTime?>("FeasibilityStudyReplyTime")).ToString("yyyy-MM-dd"),//可研批复时间
FeasibilityStudyReplyCode = dr.Field<string>("FeasibilityStudyReplyCode"),//可研批复文号
FeasibilityStudyReplyCodeAttach = dr.Field<string>("FeasibilityStudyReplyCodeAttach"),//可研批复文号附件
//概算
ApproximateReplyTime = dr.Field<DateTime?>("ApproximateReplyTime") == null ? "" : Convert.ToDateTime(dr.Field<DateTime?>("ApproximateReplyTime")).ToString("yyyy-MM-dd"),//概算批复时间
ApproximateReplyCode = dr.Field<string>("ApproximateReplyCode"),//概算批准文号
ApproximateReplyCodeAttach = dr.Field<string>("ApproximateReplyCodeAttach"),//概算批准文号附件
ApproximateExamApprovalMoney = dr.Field<decimal?>("ApproximateExamApprovalMoney") ?? 0,//概算审批金额
//招投标项目信息核准招标方式表
ApprovedInviteBidModeTime = dr.Field<DateTime?>("ApprovedInviteBidModeTime") == null ? "" : Convert.ToDateTime(dr.Field<DateTime?>("ApprovedInviteBidModeTime")).ToString("yyyy-MM-dd"),//核准招标方式时间
ApprovedInviteBidModeCode = dr.Field<string>("ApprovedInviteBidModeCode"),//核准招标方式文号
ApprovedInviteBidModeMoney = dr.Field<decimal?>("ApprovedInviteBidModeMoney") ?? 0,//招标方式核准金额
ApprovedInviteBidModeBasisAttach = dr.Field<string>("ApprovedInviteBidModeBasisAttach"),//上传核准招标方式依据文件
IsEvaluate = dr.Field<bool?>("IsEvaluate") ?? false,//项目投资是否评审
ApprovedInviteBidModeBasis = dr.Field<string>("ApprovedInviteBidModeBasis"),//上传核准招标方式依据
//招投标项目信息结算表
FinalAccountMoney = dr.Field<decimal?>("FinalAccountMoney") ?? 0,//决算金额
ApproximateExecMoney = dr.Field<decimal?>("ApproximateExecMoney") ?? 0,//执行金额
IsExceedApproximate = dr.Field<bool?>("IsExceedApproximate") ?? false,//是否超出概算
ExceedApproximateMoney = dr.Field<decimal?>("ExceedApproximateMoney") ?? 0,//超出概算金额
//
PackageID = dr.Field<Guid?>("PackageID"),//包类型
PackageClassID = dr.Field<Guid?>("PackageClassID"),//包类型
EngineeringName = dr.Field<string>("EngineeringName"),
AgencyName = dr.Field<string>("AgencyName"),
InviteSchemeSancDept = dr.Field<string>("InviteSchemeSancDept"),
SanctionPPMode = dr.Field<Guid?>("SanctionPPMode"),
SanctionPPModeText = (tp1 == null ? "" : tp1.Title),
RealPPMode = dr.Field<Guid?>("RealPPMode"),
RealPPModeText = (tp2 == null ? "" : tp2.Title),
PPChangeSancDept = dr.Field<string>("PPChangeSancDept"),
PPChangeReason = dr.Field<string>("PPChangeReason"),
PPChangeBasis = dr.Field<string>("PPChangeBasis"),
PPChangeBasisAttach = dr.Field<string>("PPChangeBasisAttach"),
Media = b_common.TranslateMedia(list_media, dr.Field<string>("Media")),
//3
SignedContractTime = dr.Field<DateTime?>("SignedContractTime") == null ? "" : Convert.ToDateTime(dr.Field<DateTime?>("SignedContractTime")).ToString("yyyy-MM-dd"),
SignedContractMoney = dr.Field<decimal?>("SignedContractMoney") ?? 0,
ExecuteUnit = dr.Field<string>("ExecuteUnit"),
//3
SettlementMoney = dr.Field<decimal?>("SettlementMoney") ?? 0,
IsExceedApproximateForPackage = dr.Field<bool?>("IsExceedApproximateForPackage") ?? false,
ExceedApproximateBasis = dr.Field<string>("ExceedApproximateBasis"),
ExceedApproximateBasisAttach = dr.Field<string>("ExceedApproximateBasisAttach"),
Note = dr.Field<string>("Note")
}
).ToList();