几天来，我一直在努力解决这个问题，并且有很多关于工作单元和 TransactionScope 的教程，但我找不到任何关于这两者的内容。非常感谢任何帮助！
我正在使用具有工作单元模式的实体框架和每种类型的存储库。根据下面的简单代码，我有一个 Member 和 MembershipDefinition 实体。我想创建一个将两者联系起来的 Membership 实体，但是当我创建 Membership 对象时，我想根据一些业务逻辑查询 DB 的最大值。因此，在我的线程将 Membership 对象写回数据库之前，我需要使用某种数据库事务来防止另一个线程增加数据库中的值。
如果我使用存储过程，这将非常简单，但我无法弄清楚如何使用纯 c# 来做到这一点......
下面的代码在数据库中创建了 100 个具有重复 MembershipNumbers 的 Membership 实体。我需要使用事务来确保在 c# 代码中生成的所有会员编号都是唯一的。
class Program
{
static void Main(string[] args)
{
var p = new Program();
p.Go();;
}
public void Go()
{
long memberId;
long membershipDefId;
using(var unitOfWork = new UnitOfWork())
{
// Setup - create test club and member entities
var testUsername = ("TestUserName" + Guid.NewGuid()).Substring(0, 29);
var member = new Member()
{
UserName = testUsername
};
var testmemebrshpDefName = ("TestMembershipDef" + Guid.NewGuid()).Substring(0, 29);
var membershipDefinition = new ClubMembershipDefinition()
{
ClubId = 1,
Name = testmemebrshpDefName
};
unitOfWork.MemberRepository.Add(member);
unitOfWork.MembershipDefinitionRepository.Add(membershipDefinition);
unitOfWork.Save();
memberId = member.Id;
membershipDefId = membershipDefinition.Id;
}
Task[] tasks = new Task[100];
// Now try to add a membership to the Member object, linking it to the test Club's single Club Definition
for (int i = 0; i < 100; i++)
{
var task = new Task(() => CreateMembership(memberId, membershipDefId));
tasks[i] = task;
task.Start();
}
Task.WaitAll(tasks);
}
private void CreateMembership(long memberId, long membershipDefId)
{
using (var unitOfWork = new UnitOfWork())
{
var member = unitOfWork.MemberRepository.GetById(memberId);
var membershipDef = unitOfWork.MembershipDefinitionRepository.GetById(membershipDefId);
var membership = new ClubMembership()
{
ClubMembershipDefinition = membershipDef
};
membership.MembershipNumber = (unitOfWork.MembershipRepository.GetMaxMembershipNumberForClub(membershipDef.ClubId) ?? 0) + 1;
member.ClubMemberships.Add(membership);
unitOfWork.Save();
}
}
}
public class UnitOfWork : IUnitOfWork, IDisposable
{
internal ClubSpotEntities _dbContext = new ClubSpotEntities();
internal MemberRepository _memberRepository;
internal MembershipRepository _membershipRepository;
internal MembershipDefinitionRepository _membershiDefinitionpRepository;
public MemberRepository MemberRepository
{
get
{
if (_memberRepository == null)
_memberRepository = new MemberRepository(_dbContext);
return _memberRepository; ;
}
}
public MembershipRepository MembershipRepository
{
get
{
if (_membershipRepository == null)
_membershipRepository = new MembershipRepository(_dbContext);
return _membershipRepository; ;
}
}
public MembershipDefinitionRepository MembershipDefinitionRepository
{
get
{
if (_membershiDefinitionpRepository == null)
_membershiDefinitionpRepository = new MembershipDefinitionRepository(_dbContext);
return _membershiDefinitionpRepository; ;
}
}
public virtual int Save()
{
return _dbContext.SaveChanges();
}
private bool _disposed = false;
protected virtual void Dispose(bool disposing)
{
if (!this._disposed)
{
if (disposing)
{
_dbContext.Dispose();
}
}
this._disposed = true;
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
}
public class MembershipRepository
{
ClubSpotEntities _dbContext = new ClubSpotEntities();
public MembershipRepository(){}
public MembershipRepository(ClubSpotEntities dbContext)
{
_dbContext = dbContext;
}
public IEnumerable<ClubMembership> GetAll()
{
return _dbContext.Set<ClubMembership>().ToList<ClubMembership>();
}
public ClubMembership GetById(long id)
{
return _dbContext.ClubMemberships.First(x => x.Id == id);
}
public long? GetMaxMembershipNumberForClub(long clubId)
{
return _dbContext.ClubMemberships.Where(x => x.ClubMembershipDefinition.ClubId == clubId).Max(x => x.MembershipNumber);
}
public ClubMembership Add(ClubMembership entity)
{
return _dbContext.Set<ClubMembership>().Add(entity);
}
public void Delete(ClubMembership membership)
{
_dbContext.Set<ClubMembership>().Remove(membership);
}
public void Save()
{
_dbContext.SaveChanges();
}
}
public partial class ClubMembership
{
public long Id { get; set; }
public long MembershipDefId { get; set; }
public Nullable<long> MemberId { get; set; }
public Nullable<long> MembershipNumber { get; set; }
public virtual ClubMembershipDefinition ClubMembershipDefinition { get; set; }
public virtual Member Member { get; set; }
}
public partial class ClubMembershipDefinition
{
public ClubMembershipDefinition()
{
this.ClubMemberships = new HashSet<ClubMembership>();
}
public long Id { get; set; }
public long ClubId { get; set; }
public string Name { get; set; }
public virtual ICollection<ClubMembership> ClubMemberships { get; set; }
}
public partial class Member
{
public Member()
{
this.ClubMemberships = new HashSet<ClubMembership>();
}
public long Id { get; set; }
public string UserName { get; set; }
public virtual ICollection<ClubMembership> ClubMemberships { get; set; }
}