EF DbContext 不一致

Question

我有以下 class:

public class ATMClient
{
    private ATMDbContext dbContext;
    private IOutputProvider outputProvider;

    public ATMClient(ATMDbContext dbContext)
        : this(dbContext, new ConsoleOutputProvider())
    {
    }

    public ATMClient(ATMDbContext dbContext, IOutputProvider outputProvider)
    {
        this.dbContext = dbContext;
        this.outputProvider = outputProvider;
    }

    public void WithdrawMoney(string cardNumber, string cardPIN, decimal money)
    {
        using (var transaction = dbContext.Database.BeginTransaction(IsolationLevel.RepeatableRead))
        {
            var currentAccount = dbContext.CardAccounts.Where(x => x.CardNumber == cardNumber).FirstOrDefault();

            try
            {
                currentAccount.CardCash -= money;

                throw new ArgumentException("On purpose exception");

                ...

                dbContext.SaveChanges();
                transaction.Commit();
            }
            catch (Exception ex)
            {                    
                outputProvider.PrintLine(ex.Message);
                transaction.Rollback();
                dbContext = new ATMDbContext();
            }

            Console.WriteLine();
            Console.WriteLine("On context recreation: ");
            Console.WriteLine("----------------------------");
            Console.WriteLine(dbContext.CardAccounts.FirstOrDefault(x => x.CardNumber == cardNumber).CardCash);
            Console.WriteLine("----------------------------");
            Console.WriteLine();
        }       
    }
}

我正在使用以下方法进行测试：

public static void Main()
{
    var dbContext = new ATMDbContext();
    var atm = new ATMClient(dbContext);

    var account = dbContext.CardAccounts.Where(x => x.CardCash >= 10000).FirstOrDefault();

    Console.WriteLine();
    Console.WriteLine("Before withdraw: ");
    Console.WriteLine("-----------------------------------");
    Console.WriteLine(account.CardNumber);
    Console.WriteLine(account.CardCash);
    Console.WriteLine("-----------------------------------");
    Console.WriteLine();

    atm.WithdrawMoney(account.CardNumber, account.CardPIN, 10000m);

    account = dbContext.CardAccounts.Where(x => x.CardNumber == account.CardNumber).FirstOrDefault();

    Console.WriteLine();
    Console.WriteLine("After withdraw: ");
    Console.WriteLine("-----------------------------------");
    Console.WriteLine(account.CardNumber);
    Console.WriteLine(account.CardCash);
    Console.WriteLine("-----------------------------------");
    Console.WriteLine();
}

我得到的最终结果：

Before withdraw:
-----------------------------------
0030972041
224027.53
-----------------------------------
On purpose exception

On context recreation: 
----------------------------
224027.53
----------------------------

After withdraw:
-----------------------------------
0030972041
214027.53
-----------------------------------

出于某种原因，"after withdraw" 打印使用了不正确的上下文，即使我已经在 Withdraw 方法中重新创建了它。这种行为的原因可能是什么？

Answer 1

我不知道您要实现什么行为，但我怀疑您希望 Main 方法中局部变量的上下文发生变化，因为您将它作为参数传递给了构造函数。这不是引用的工作方式。当您将引用作为参数传递时，会将引用的副本提供给方法。如果它被另一个引用替换，则原始变量不会改变。在 Main 方法中，您仍然使用在第一行初始化的对象。

如果您希望该方法能够更改引用，您应该将参数声明为 "ref"，但我怀疑这是您想要实现的任何目标的最佳解决方案。

EF DbContext 不一致

EF DbContext incosistency

c#

sql-server

entity-framework