4

我正在插入大约 6 家银行的 5000 笔交易，但我在数据库中获得了 5000 行名称重复的银行行。

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;
    }
}

然后插入我正在循环一些数据并因此插入：

        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();
        }

看起来该FindOrInsertBank方法一直在访问数据库，而不是在本地查看它最近添加的内容，而不是承诺的银行。我怎么能/应该这样做？

我应该SaveChanges在每个银行插入之后吗？不是我真正想做的，我希望这只是一笔交易。

4

2 回答 2

2

您可以尝试查询更改跟踪器（这是一个内存查询，而不是数据库查询）：

using (var context = new FinancialRecordContext())
{
    foreach (var t in data)
    {
        Bank bank = context.ChangeTracker.Entries()
            .Where(e => e.Entity is Bank && e.State != EntityState.Deleted)
            .Select(e => e.Entity as Bank)
            .SingleOrDefault(b => b.Name == t.BankName);

        if (bank == null)
            bank = context.FindOrInsertBank(t.BankName);

        var tran = new Transaction
        {
            Description = t.Description,
            Value = t.Value,
            TransDate = t.TransDate,
            Bank = bank
        };
        context.Transactions.Add(tran);
    }
    context.SaveChanges();
}

编辑

在此处使用更改跟踪器可能对性能不利，因为Bank.Name它不是实体的键，我猜查询将是对条目的线性搜索。在这种情况下，使用手写字典可能是更好的解决方案：

using (var context = new FinancialRecordContext())
{
    var dict = new Dictionary<string, Bank>();
    foreach (var t in data)
    {
        Bank bank;
        if (!dict.TryGetValue(t.BankName, out bank))
        {
            bank = context.FindOrInsertBank(t.BankName);
            dict.Add(t.BankName, bank);
        }

        var tran = new Transaction
        {
            Description = t.Description,
            Value = t.Value,
            TransDate = t.TransDate,
            Bank = bank
        };
        context.Transactions.Add(tran);
    }
    context.SaveChanges();
}
于 2013-04-13T13:52:57.257 回答
2

有几个建议可以尝试：

1）首先检查Local集合DbSet<Bank>。

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;
}

DetectChanges()2）每次更新后强制调用

context.Transactions.Add(tran);
context.ChangeTracker.DetectChanges();
于 2013-04-13T14:19:49.013 回答