类型'System.ObjectDisposedException'的异常

Question

我有以下EF代码的第一个代码.它工作正常.但当我寻找'club2.Members'的价值时,它会说:

'club2.Members'抛出了'System.ObjectDisposedException'类型的异常.

消息是:

ObjectContext实例已被释放,不能再用于需要连接的操作.

我没有为Members属性设置值.没关系.但是它不应该在内部引起任何异常.

1. 有没有办法克服这个例外？
2. 删除此异常是否有助于提高性能？
3. 为什么这个异常不会导致程序执行终止？

注意:我不需要俱乐部实体中的会员数据(在我打电话的时候).即使当时没有成员加入俱乐部.我只需要摆脱异常; 不使用预先加载来加载数据.如何避免异常？

namespace LijosEF
{

public class Person
{
    public int PersonId { get; set; }
    public string PersonName { get; set; }
    public virtual ICollection<Club> Clubs { get; set; }
}

public class Club 
{
    public int ClubId { get; set; }
    public string ClubName { get; set; }
    public virtual ICollection<Person> Members { get; set; }

}




//System.Data.Entity.DbContext is from EntityFramework.dll
public class NerdDinners : System.Data.Entity.DbContext
{

    public NerdDinners(string connString): base(connString)
    { 

    }

    protected override void OnModelCreating(DbModelBuilder modelbuilder)
    {
         //Fluent API - Plural Removal
        modelbuilder.Conventions.Remove<PluralizingTableNameConvention>();
    }

    public DbSet<Person> Persons { get; set; }
    public DbSet<Club> Clubs { get; set; }



}
}




    static void Main(string[] args)
    {
        Database.SetInitializer<NerdDinners>(new MyInitializer());

        CreateClubs();
        CreatePersons();

    }

    public static void CreateClubs()
    {

        string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
        using (var db = new NerdDinners(connectionstring))
        {

            Club club1 = new Club();
            club1.ClubName = "club1";

            Club club2 = new Club();
            club2.ClubName = "club2";

            Club club3 = new Club();
            club3.ClubName = "club3";

            db.Clubs.Add(club1);
            db.Clubs.Add(club2);
            db.Clubs.Add(club3);

            int recordsAffected = db.SaveChanges();


        }
    }

    public static Club GetClubs(string clubName)
    {
        string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
        using (var db = new NerdDinners(connectionstring))
        {

            var query = db.Clubs.SingleOrDefault(p => p.ClubName == clubName);
            return query;
        }
    }

    public static void CreatePersons()
    {
        string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
        using (var db = new NerdDinners(connectionstring))
        {

            Club club1 = GetClubs("club1");
            Club club2 = GetClubs("club2");
            Club club3 = GetClubs("club3");

             //More code to be added (using db) to add person to context and save
        }
    }

Answer 1

您收到此错误是因为您在执行查询后处置dbcontext.如果要使用"成员"中的数据,请使用查询加载它:http: //blogs.msdn.com/b/adonet/archive/2011/01/31/using-dbcontext-in-ef-feature- CTP5部分-6加载相关-entities.aspx

如果您不需要延迟加载,这意味着只加载您在查询中加载的数据(这将消除异常),请设置LazyLoadingEnabled = false.请在此处查看: 默认情况下,在Entity Framework 4中禁用延迟加载