Check if Record Exists in Entity Framework [duplicate]

问题

Could somebody please tell me how I check to see if a record exists, if it does exists then do nothing and if it doesn't then add the record to the database?

Please see my code below:

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();
    }
}

I just want to ensure no possible duplication in the database.

回答1:

Use 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();
    }
}

回答2:

using (WebApplication1Entities db = new WebApplication1Entities())
{
   var order = db.Orders.GetAll().Where(x=> x.Transaction == txnId).FirstOrDefault();
   if(order != null) // update
   {
      //.....
      db.SaveChanges();
    }
   else
   {
      // new
   }
}

来源：https://stackoverflow.com/questions/23654057/check-if-record-exists-in-entity-framework

标签

entity-framework