在自定义RoleProvider中首先使用EF代码导致许多数据访问异常的原因是什么？

Question

我的角色提供者看起来像下面的类(删节).我在VS 2012上运行IIS Express和SQL 2012 Express,我在这个角色提供程序代码中得到了许多看似随机的异常.

public class Educ8RoleProvider : RoleProvider
{
    private readonly Educ8DbContext _dbContext = new Educ8DbContext();
    private readonly Authorization _authorization;
    public Educ8RoleProvider()
    {
        _authorization = new Authorization(_dbContext);
    }
    public override void Initialize(string name, System.Collections.Specialized.NameValueCollection config)
    {
        try
        {
            base.Initialize(name, config);
        }
        catch (Exception ex)
        {
            ErrorSignal.FromCurrentContext().Raise(ex);
            throw;
        }
    }
    public override bool IsUserInRole(string username, string roleName)
    {
        return GetRolesForUser(username).Any(r => r.ToLower() == roleName);
    }
    public override string[] GetRolesForUser(string username)
    {
        return _authorization.GetRolesForMember(username).Select(r => r.Name).ToArray();
    }
}

这是我Authorization班级的一个例子:

public class Authorization
{
    private readonly Educ8DbContext _dbContext;
    private readonly IMemberRepository _memberRepository;
    private readonly IRoleRepository _roleRepository;
    private readonly IMemberRoleRepository _memberRoleRepository;
    public Authorization(Educ8DbContext context)
    {
        _dbContext = context;
        _memberRepository = new MemberRepository(_dbContext);
        _roleRepository = new RoleRepository(_dbContext);
        _memberRoleRepository = new MemberRoleRepository(_dbContext);
    }
    public IQueryable<Role> GetRoles()
    {
        return _roleRepository.ListAll();
    }
    public IQueryable<Role> GetRolesForMember(int memberId)
    {
        var roleIds = _memberRoleRepository.ListAll()
            .Where(mr => mr.MemberId == memberId)
            .Select(mr => mr.RoleId);
        return _roleRepository.ListAll()
            .Where(r => roleIds.Contains(r.Id));
    }
}

我每小时得到大约两到三个以下异常.重新启动项目会立即解决问题,直到下一个问题.

• 不允许更改'ConnectionString'属性.连接的当前状态已关闭.
• 在创建模型时不能使用上下文.
• 底层提供程序在Open上失败.

值得注意的是,我在项目的其他任何地方都存在绝对零数据访问问题.

关于可能导致这种情况的任何建议都会受到欢迎.

Answer 1

Gert Arnold的评论是正确的.你必须意识到RoleProvider作为单身人士的奔跑.每次重新启动应用程序时,都会导致构建此类的新实例.只要您的应用程序正在运行,它就会继续使用这个单一实例.

在我意识到这个类以单例形式运行之前,我曾经遇到过与你问题相同的异常.掌握了这些知识之后,让这些例外消失并不困难:

public class Educ8RoleProvider : RoleProvider
{
    //private readonly Educ8DbContext _dbContext = new Educ8DbContext();
    //private readonly Authorization _authorization;
    public Educ8RoleProvider()
    {
        //_authorization = new Authorization(_dbContext);
    }

    private Authorization GetAuthorization()
    {
        return new Authorization(new Educ8DbContext());
    }

    public override void Initialize(string name, NameValueCollection config)
    {
        try
        {
            base.Initialize(name, config);
        }
        catch (Exception ex)
        {
            ErrorSignal.FromCurrentContext().Raise(ex);
            throw;
        }
    }
    public override bool IsUserInRole(string username, string roleName)
    {
        return GetRolesForUser(username)
            .Any(r => r.ToLower() == roleName);
    }
    public override string[] GetRolesForUser(string username)
    {
        return GetAuthorization().GetRolesForMember(username)
            .Select(r => r.Name).ToArray();
    }
}

从本质上讲,您希望确保每个方法调用RoleProvider一个全新的DbContext实例.这样,RoleProvider单身人士就不会挂在一个DbContext陈旧的单身上.