检查实体框架中是否存在记录

Question

有人可以告诉我如何检查记录是否存在,如果它确实存在然后什么也不做,如果没有,那么将记录添加到数据库中？

请参阅下面的代码:

if (isIpnValidated == true)
{
    using (WebApplication1Entities db = new WebApplication1Entities())
    {
        Orders order = new Orders();
        order.UserId = userId;
        order.Date = System.DateTime.Now;
        order.Transaction = txnId;
        order.Amount = Convert.ToDecimal(mcGross);
        order.Email = payerEmail;
        order.Country = residenceCountry;

        db.Orderss.Add(order);
        db.SaveChanges();
    }
}

我只是想确保数据库中没有可能的重复.

Answer 1

用途Any:

if (isIpnValidated == true)
{
    using (WebApplication1Entities db = new WebApplication1Entities())
    {
        if (db.Orderss.Any(o => o.Transaction == txnId)) return;

        Orders order = new Orders();
        order.UserId = userId;
        order.Date = System.DateTime.Now;
        order.Transaction = txnId;
        order.Amount = Convert.ToDecimal(mcGross);
        order.Email = payerEmail;
        order.Country = residenceCountry;

        db.Orderss.Add(order);
        db.SaveChanges();
    }
}