我写了一个代码，从2个不同的数据库返回一个列表。这两个dbcontext之间的联合字段是accountid和email（两者具有相同的值）。由于有2个不同的数据库，我不能在实体框架中使用join。所以我使用嵌套使用和每个块。这是我的代码：
namespace AdminMvc.Components.BankDepositHistory
{
public class BankDepositHistoryHelper
{
public static List<BankDepositHistoryItemDto> GetChangeRequestsList(int skip, int take, out int total, string name, string email, AvailableBankDepositStates state)
{
using (var myketAdsDB = new MyketAdsEntities())
{
using (var myketDB = new MyketReadOnlyDb())
{
#region DefaultQuery
var bankDepositHistories = myketAdsDB.BankDepositHistories.AsQueryable();
#endregion
#region Filtering
if (!string.IsNullOrWhiteSpace(name))
{
var emails = myketDB.AppDevelopers
.Where(n => n.RealName.Contains(name))
.Select(e => e.Email).ToList();
// emails.Add(email);
if (emails.Count > 0)
{
bankDepositHistories = bankDepositHistories.Where(e => emails.Contains(e.AccountId));
}
}
if (!string.IsNullOrWhiteSpace(email))
{
bankDepositHistories = bankDepositHistories.Where(a => a.AccountId.Contains(email));
}
if (state != AvailableBankDepositStates.All)
{
bankDepositHistories = state == AvailableBankDepositStates.Success ?
bankDepositHistories.Where(x => x.State == AvailableBankDepositStates.Success.ToString()) :
bankDepositHistories.Where(x => x.State == AvailableBankDepositStates.Fail.ToString());
}
else
{
bankDepositHistories = bankDepositHistories.
Where(x => x.State != BankDepositState.Start.ToString());
}
#endregion
#region GetingTotalpages
total = bankDepositHistories.Count();
#endregion
#region Pagination
var pageResult = bankDepositHistories.OrderByDescending(ba => ba.CreationDate).Skip(skip).Take(take).ToList();
#endregion
#region FillingDomainObjects
var emailFilter = pageResult.Select(r => r.AccountId).ToList();
var developers = myketDB.AppDevelopers.Where(a => emailFilter.Contains(a.Email)).
Select(r => new { r.RealName, r.Email }).ToList();
var result = pageResult
.Select(b => new BankDepositHistoryItemDto()
{
Id = b.Id,
AccountId = b.AccountId,
Amount = b.Amount,
ClientIp = b.ClientIp,
State = (BankDepositState)Enum.Parse(typeof(BankDepositState), b.State, true),
ReturnUrl = b.ReturnUrl,
AdditionalData = b.AdditionalData,
Gateway = b.Gateway,
CreationDate = b.CreationDate,
PaymentRefNumber = b.PaymentRefNumber,
Uuid = b.Uuid,
}).ToList();
foreach (var bankDepositHistory in result)
{
foreach (var developer in developers)
{
if (bankDepositHistory.AccountId == developer.Email)
{
bankDepositHistory.RealName = developer.RealName;
}
}
}
return result;
#endregion
}
}
}
我想知道是否可以避免使用嵌套使用并为每个数据库写一个单独的使用。
你的代码非常错综复杂。这是我可以做的最好的分离和简化：
public static List<BankDepositHistoryItemDto> GetChangeRequestsList(int skip, int take, out int total, string name, string email, AvailableBankDepositStates state)
{
var statesFilter = new Dictionary<AvailableBankDepositStates, Func<IQueryable<BankDepositHistory>, IQueryable<BankDepositHistory>>>()
{
{ AvailableBankDepositStates.All, bdh => bdh.Where(x => x.State != BankDepositState.Start.ToString()) },
{ AvailableBankDepositStates.Success, bdh => bdh.Where(x => x.State == AvailableBankDepositStates.Success.ToString()) },
{ AvailableBankDepositStates.Fail, bdh => bdh.Where(x => x.State == AvailableBankDepositStates.Fail.ToString()) },
};
List<string> emails = new List<string>();
ILookup<string, string> developers = null;
using (var myketDB = new MyketReadOnlyDb())
{
if (!string.IsNullOrWhiteSpace(name))
{
emails = myketDB.AppDevelopers.Where(n => n.RealName.Contains(name)).Select(e => e.Email).ToList();
}
developers = myketDB.AppDevelopers.ToLookup(x => x.Email, x => x.RealName);
}
using (var myketAdsDB = new MyketAdsEntities())
{
var bankDepositHistories = myketAdsDB.BankDepositHistories.AsQueryable();
if (emails.Count() > 0)
{
bankDepositHistories = bankDepositHistories.Where(e => emails.Contains(e.AccountId));
}
if (!string.IsNullOrWhiteSpace(email))
{
bankDepositHistories = bankDepositHistories.Where(a => a.AccountId.Contains(email));
}
bankDepositHistories = statesFilter[state](bankDepositHistories);
total = bankDepositHistories.Count();
var result =
bankDepositHistories
.OrderByDescending(ba => ba.CreationDate)
.Skip(skip)
.Take(take)
.ToList()
.Select(b => new BankDepositHistoryItemDto()
{
Id = b.Id,
AccountId = b.AccountId,
Amount = b.Amount,
ClientIp = b.ClientIp,
State = (BankDepositState)Enum.Parse(typeof(BankDepositState), b.State, true),
ReturnUrl = b.ReturnUrl,
AdditionalData = b.AdditionalData,
Gateway = b.Gateway,
CreationDate = b.CreationDate,
PaymentRefNumber = b.PaymentRefNumber,
Uuid = b.Uuid,
RealName = developers[b.AccountId].LastOrDefault(),
}).ToList();
return result;
}
}
这是我必须安全地编写的代码：
public enum AvailableBankDepositStates
{
All, Success, Fail
}
public enum BankDepositState
{
Start
}
public class BankDepositHistoryItemDto
{
public string AccountId;
public BankDepositState State;
public DateTime CreationDate;
public string RealName;
}
public class MyketAdsEntities : IDisposable
{
public IEnumerable<BankDepositHistory> BankDepositHistories;
public void Dispose()
{
throw new NotImplementedException();
}
}
public class MyketReadOnlyDb : IDisposable
{
public IEnumerable<AppDeveloper> AppDevelopers;
public void Dispose()
{
throw new NotImplementedException();
}
}
public class BankDepositHistory
{
public string AccountId;
public string State;
public DateTime CreationDate;
}
public class AppDeveloper
{
public string RealName;
public string Email;
}
你可以做你想要的。内部使用的电子邮件列表会影响bankDepositHistories，它们来自外部使用，但是外部查询直到稍后才会执行。 （另外，原始内部使用不依赖于外部的任何东西，因此可以移动到外部）。
因此，首先使用myketDB获取电子邮件列表：
List<Email> emails = new List<Email>();
using (var myketDB = new MyketReadOnlyDb())
{
if (!string.IsNullOrWhiteSpace(name))
{
emails = myketDB.AppDevelopers
.Where(n => n.RealName.Contains(name))
.Select(e => e.Email).ToList();
}
}
// original outer using is now after the above
然后通过在上面的使用下方的原始代码中移动外部使用myketAdsDB来执行所有其他逻辑。现在这是一个接一个，而不是嵌套。
如果您正在执行的操作不必是事务性的，则首选顺序访问上下文是首选，因为您无需无理由延长外部上下文的生命周期。在外部内部运行可延长外部的使用寿命。