c# - Entity Framework 6 错误服务器版本 : (System. Data.SqlClient.SqlConnection)customerOrderContext.Database.Connection).ServerVersion

Question

我正在实现一个将使用 Entity Framework 6 获取数据的 Web API。我正在使用 Sql Server 2014 和 visual studio 2015。在调试 CustomerDao 类中的代码时，我在 customerOrderContext 对象中看到了一个异常，尽管我可以查看客户对象中的记录。但是在执行 using block 后，我看不到任何记录。

((System.Data.SqlClient.SqlConnection)customerOrderContext.Database.Connection).ServerVersion

CustomerDao

using (var customerOrderContext = new Entities())
                {
                    return (from customer in customerOrderContext.Customers

                            select new CustomerOrder.BusinessObjects.Customers
                            {
                                Id = customer.Id,
                                FirstName = customer.FirstName,
                                LastName = customer.LastName,
                                Address = customer.Address,
                                City = customer.City,
                                Email = customer.Email,
                                Gender = customer.Gender,
                                State = customer.State,
                                Zip = customer.Zip
                            }).ToList();
                }

config文件中的连接字符串如下

<add name="Entities" connectionString="metadata=res://*/EF.CustomerOrderContext.csdl|res://*/EF.CustomerOrderContext.ssdl|res://*/EF.CustomerOrderContext.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=Tom-PC\MSSQLSERVER2014;initial catalog=Ransang;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

上下文类如下

public partial class Entities : DbContext
{
    public Entities()
        : base("name=Entities")
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

    }

    public virtual DbSet<Customer> Customers { get; set; }
    public virtual DbSet<OrderDetail> OrderDetails { get; set; }
    public virtual DbSet<Order> Orders { get; set; }
    public virtual DbSet<Product> Products { get; set; }
}

CustomProvider.cs

  public IEnumerable<BusinessObjects.Customers> GetAllCustomers()
        {
            IList<BusinessObjects.Customers> customerCollection = new List<BusinessObjects.Customers>();
            dataAccess.CustomerDao.GetAllCustomers();
            return customerCollection;
        }

Answer 1

异常(exception)是documented这是因为连接已关闭。这没有问题。

但显然你得到的结果是空的，因为你没有使用结果，你只是返回 new List<BusinessObjects.Customers>()在你的方法中:

public IEnumerable<BusinessObjects.Customers> GetAllCustomers()
{
    IList<BusinessObjects.Customers> customerCollection = 
        new List<BusinessObjects.Customers>(); // ← An empty list
    dataAccess.CustomerDao.GetAllCustomers();  // ← Just executed but didn't use anywhere
    return customerCollection;                 // ← The empty list you created at first
}

您需要 return dataAccess.CustomerDao.GetAllCustomers(); :