c# - 我应该如何防止在这里多次插入？

Question

我插入了大约 6 家银行的 5000 笔交易，但我在数据库中得到了 5000 行名称重复的银行。

public class Transaction
{
    [Key]
    public int Id { get; set; }
    public DateTime TransDate { get; set; }
    public decimal Value { get; set; }
    public string Description { get; set; }
    public Bank Bank { get; set; }
}

public class Bank
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
}

public class FinancialRecordContext : DbContext
{
    public FinancialRecordContext() : base("FinancialRecordDatabase") { }

    public DbSet<Transaction> Transactions { get; set; }

    public DbSet<Bank> Banks { get; set; }

    public Bank FindOrInsertBank(string bankName)
    {
        var bank = Banks.SingleOrDefault(b => b.Name == bankName);
        if (bank == null)
        {
            bank = new Bank { Name = bankName };
            Banks.Add(bank);
        }
        return bank;
    }
}

然后为了插入，我正在循环遍历一些数据并插入:

        using (var context = new FinancialRecordContext())
        {
            foreach (var t in data)
            {
                var tran = new Transaction
                {
                    Description = t.Description,
                    Value = t.Value,
                    TransDate = t.TransDate,
                    Bank = context.FindOrInsertBank(t.BankName)
                };
                context.Transactions.Add(tran);
            }
            context.SaveChanges();
        }

FindOrInsertBank 方法似乎一直在访问数据库，而不是在本地查看最近添加的但不是已提交的银行。我怎么能/应该这样做？

我是否应该在每次插入银行后SaveChanges？这不是我真正想要做的，我希望这一切都是一笔交易。

Answer 1

一些尝试的建议:

1) 检查Local收藏DbSet<Bank>首先。

public Bank FindOrInsertBank(string bankName)
{
    var bank = Banks.Local.SingleOrDefault(b => b.Name == bankName);
    if (bank == null)
    {
        var bank = Banks.SingleOrDefault(b => b.Name == bankName);
        if (bank == null)
        {
            bank = new Bank { Name = bankName };
            Banks.Add(bank);
        }
    }
    return bank;
}

2) 强制调用 DetectChanges()每次更新后

context.Transactions.Add(tran);
context.ChangeTracker.DetectChanges();