EntityReference - EntityKey，它们是什么，如何使用它们，以及我们何时需要它们？

Question

我想了解下面的代码，但找不到有关EntityReference＆amp; amp;互联网上的EntityKey。下面的代码做了什么？

编辑：我意识到这是与外键相关的东西，我正在进一步调查。

Employee e = db.Employee.FirstOrDefault((Employee x) => x.Reference == data.EmployeeReference);
e.LocationReference.EntityKey = new EntityKey("FlexibleBenefitsDb.Location", "ID", xpatLocationID);

和

public EntityReference<Location> LocationReference
{
    get
    {
        return ((IEntityWithRelationships)this).RelationshipManager.GetRelatedReference<Location>("Nestle.FlexibleBenefits.Model.EmployeeLocation", "Location");
    }
    set
    {
        if (value != null)
        {
            ((IEntityWithRelationships)this).RelationshipManager.InitializeRelatedReference<Location>("Nestle.FlexibleBenefits.Model.EmployeeLocation", "Location", value);
        }
    }
}

有关完整的源代码，请查看以下内容：

完整代码：

using Nestle.FlexibleBenefits.Business;
using Nestle.FlexibleBenefits.Business.BenefitCostCalculations;
using Nestle.FlexibleBenefits.DataAccess;
using Nestle.FlexibleBenefits.DataImport.Model;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Transactions;
namespace Nestle.FlexibleBenefits.DataImport
{
    public class FlexibleBenefitDbImporter : IBenefitImporter
    {
        public void Import(IBenefitLoader loader)
        {
            List<RawEmployeeBenefit> dataList = loader.Load();
            using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required, new TimeSpan(0, 30, 0)))
            {
                using (FlexibleBenefitsDb db = new FlexibleBenefitsDb())
                {
                    foreach (RawEmployeeBenefit data in dataList)
                    {
                        Employee e = db.Employee.FirstOrDefault((Employee x) => x.Reference == data.EmployeeReference);
                        if (e == null)
                        {
                            e = new Employee();
                            e.Reference = data.EmployeeReference;
                        }
                        e.DailyGrossSalary = data.DailyGrossSalary;
                        RawEmployeeBenefitDetail xpatCOR = data.Details.FirstOrDefault((RawEmployeeBenefitDetail x) => x.BenefitCode == "COR001" && x.Value == string.Empty);
                        RawEmployeeBenefitDetail xpatCOR2 = data.Details.FirstOrDefault((RawEmployeeBenefitDetail x) => x.BenefitCode == "COR002" && x.Value == string.Empty);
                        if (xpatCOR != null && xpatCOR2 != null)
                        {
                            int xpatLocationID = 0;
                            if (data.LocationID == 2)
                            {
                                xpatLocationID = 4;
                            }
                            else
                            {
                                if (data.LocationID == 3)
                                {
                                    xpatLocationID = 5;
                                }
                            }
                            e.LocationReference.EntityKey = new EntityKey("FlexibleBenefitsDb.Location", "ID", xpatLocationID);
                        }
                        else
                        {
                            e.LocationReference.EntityKey = new EntityKey("FlexibleBenefitsDb.Location", "ID", data.LocationID);
                        }
                        e.FirstName = data.FirstName;
                        if (data.IncomeTaxRatio > 1m)
                        {
                            data.IncomeTaxRatio /= 100m;
                        }
                        e.IncomeTaxRatio = data.IncomeTaxRatio;
                        e.LastName = data.LastName;
                        e.UserName = string.Format("{0}\\{1}", SystemProperties.DomainName, data.UserName);
                        e.MaritalStatusReference.EntityKey = new EntityKey("FlexibleBenefitsDb.MaritalStatus", "ID", data.MaritalStatusID);
                        e.MaxExchangeableLeaveDays = data.MaxExchangeableLeaveDays;
                        PrivatePensionFund privatePensionFund = db.PrivatePensionFund.FirstOrDefault((PrivatePensionFund x) => x.MaritalStatus.ID == data.MaritalStatusID && x.GrossSalaryRangeStart < e.DailyGrossSalary * 30m && x.GrossSalaryRangeEnd > e.DailyGrossSalary * 30m);
                        if (privatePensionFund == null)
                        {
                            e.MaxPrivatePensionFund = 0m;
                        }
                        else
                        {
                            e.MaxPrivatePensionFund = privatePensionFund.MaxPrivatePensionFund;
                        }
                        EmployeeBenefit eb = new EmployeeBenefit();
                        eb.Employee = e;
                        eb.BenefitAllowanceGrossTotal = 0m;
                        eb.BenefitYear = SystemProperties.ActiveTargetYear;
                        eb.CoreBenefitGrossTotal = 0m;
                        eb.IsApproved = false;
                        eb.IsModified = false;
                        eb.StoredFileReference.EntityKey = new EntityKey("FlexibleBenefitsDb.StoredFile", "ID", loader.StoredFileID);
                        foreach (RawEmployeeBenefitDetail detailData in data.Details)
                        {
                            if (!string.IsNullOrEmpty(detailData.Value))
                            {
                                EmployeeBenefitDetail ebd = new EmployeeBenefitDetail();
                                Benefit b = db.Benefit.Include("BenefitType").FirstOrDefault((Benefit bnf) => bnf.Code == detailData.BenefitCode);
                                if (b == null)
                                {
                                    throw new ApplicationException(string.Format("Invalid benefit code {0} specified", detailData.BenefitCode));
                                }
                                if (b.BenefitType.ID != 1 && b.BenefitType.ID != 2)
                                {
                                    throw new ApplicationException("Only Core and Exchangable benefits are imported. Wrong BenefitCode.");
                                }
                                ebd.Benefit = b;
                                ebd.EmployeeBenefit = eb;
                                ebd.IsExchanged = false;
                                ebd.Quantity = 0m;
                                ebd.NetCost = decimal.Parse((detailData.Value == string.Empty) ? "0" : detailData.Value);
                                if (b.ApplyIncomeTax || b.ApplySocialSecurityTax || b.ApplyStampTax)
                                {
                                    ebd.GrossCost = NetGrossCalculations.ConvertNetToGross(e, ebd.NetCost, b.ApplyStampTax, b.ApplySocialSecurityTax, b.ApplyStampTax);
                                }
                                else
                                {
                                    ebd.GrossCost = ebd.NetCost;
                                }
                                eb.BenefitAllowanceGrossTotal += ebd.GrossCost;
                                if (b.BenefitType.ID == 1)
                                {
                                    eb.CoreBenefitGrossTotal += ebd.GrossCost;
                                }
                                eb.EmployeeBenefitDetails.Add(ebd);
                            }
                        }
                    }
                    db.SaveChanges();
                    scope.Complete();
                }
            }
        }
    }
}