Question

我有一个存储库类，如下所示。有一种获取实体对象的方法 - GetPaymentByID。我正在检索Payment对象并对其PaymentType属性进行更改。但这并没有反映在数据库中。我知道原因 - SaveContextChanges方法使用新的上下文。

我需要使用每个请求的上下文方法。因此，我在每种方法中创建新的上下文。

在这种情况下，如何修改代码以成功更新数据库？

注意：客户端程序不应使用ObjectContext，因为存储库可以使用另一个不使用Entity Framework 的存储库进行更改。

注意：“ DataContext是轻量级的，创建起来并不昂贵”

namespace MyRepository
{


public class MyPaymentRepository
{
    private string connectionStringVal;
    public MyPaymentRepository()
    {
        SqlConnectionStringBuilder sqlBuilder = new SqlConnectionStringBuilder();
        sqlBuilder.DataSource = ".";
        sqlBuilder.InitialCatalog = "LibraryReservationSystem";
        sqlBuilder.IntegratedSecurity = true;

        // Initialize the EntityConnectionStringBuilder.
        EntityConnectionStringBuilder entityBuilder = new EntityConnectionStringBuilder();
        entityBuilder.Provider = "System.Data.SqlClient";
        entityBuilder.ProviderConnectionString = sqlBuilder.ToString();
        entityBuilder.Metadata = @"res://*/MyEDMtest.csdl|res://*/MyEDMtest.ssdl|res://*/MyEDMtest.msl";

        connectionStringVal = entityBuilder.ToString();
    }




    public MyEntityDataModelEDM.Payment GetPaymentByID(int paymentID)
    {
        MyEntityDataModelEDM.Payment payment;
        using (var myObjectContext2 = new MyEntityDataModelEDM.LibraryReservationSystemEntities(connectionStringVal))
        {

            Func<MyEntityDataModelEDM.Payment, bool> predicate = (p => p.PaymentID == paymentID);
            payment = myObjectContext2.Payments.SingleOrDefault(predicate);
        }
        return payment;
    }


    public void SaveContextChanges(MyEntityDataModelEDM.Payment paymentEntity)
    {
        using (var myObjectContext = new MyEntityDataModelEDM.LibraryReservationSystemEntities(connectionStringVal))
        {
            myObjectContext.SaveChanges();
        }
    }


}


}

客户端

        MyRepository.MyPaymentRepository rep = new MyRepository.MyPaymentRepository();

        MyEntityDataModelEDM.Payment p2= rep.GetPaymentByID(1);
        p2.PaymentType = "TeSSS";
        rep.SaveContextChanges(p2);

阅读

Answer 1

您需要添加（如果数据是新的）或附加（如果数据被编辑）对象到上下文：

http://blogs.msdn.com/b/adonet/archive/2011/01/29/using-dbcontext-in-ef-feature-ctp5-part-4-add-attach-and-entity-states.aspx

这些方面的东西：

public void SaveContextChanges(MyEntityDataModelEDM.Payment paymentEntity)
{
    using (var myObjectContext = new MyEntityDataModelEDM.LibraryReservationSystemEntities(connectionStringVal))
    {
        // use your own logic for determining a "new" entity
        myObjectContext.Entry(paymentEntity).State = 
                (paymentEntity.PaymentID == default(int)) ?  
                               EntityState.Added :
                               EntityState.Modified;

        myObjectContext.SaveChanges();
    }
}

每个请求的上下文：如何更新实体

1 个答案: