Autofac：如何在 SingleInstance 范围内使用每个请求的依赖关系？

Question

有IDbConnection连接依赖注册为per-request和ApplicationOAuthProvider注册为single instance。

builder.Register(c => new SqlConnection(WebConfigUtils.DefaultConnectionString))
            .As<IDbConnection>()
            .InstancePerRequest();

builder.RegisterType<ApplicationOAuthProvider>()
            .As<IOAuthAuthorizationServerProvider>()
            .PropertiesAutowired()
            .SingleInstance();

需要在身份声明中存储用户权限。为此，我创建了命令 GetRolePermissions，并在此命令中注入 IDbConnection 实例。

public class GetRolePermissions
{
    public class Command: IRequest<List<string>>
    {
        public ICollection<AspNetUserRole> UserRoles { get; set; }
    }

    public class Handler : AsyncRequestHandler<Command, List<string>>
    {
        private IDbConnection databaseConnection;

        public Handler(IDbConnection databaseConnection)
        {
            this.databaseConnection = databaseConnection;
        }
    }
}

这个命令正在ApplicationOAuthProvider中创建

public class ApplicationOAuthProvider : OAuthAuthorizationServerProvider
{
    private async Task<ClaimsIdentity> GenerateUserIdentityAsync(AspNetUser user, string authenticationType)
    {
        user.SecurityStamp = Guid.NewGuid().ToString();
        var identity = await mediator.Send(new GenerateUserIdentity.Command
        {
            AuthenticationType = authenticationType,
            User = user
        });

        List<string> permissions = null;
        permissions = await mediator.Send(new GetRolePermissions.Command { UserRoles = user.Roles });
        var permissionClaimValue = permissions != null && permissions.Count > 0
            ? permissions.Aggregate((resultString, permission) => resultString + "," + permission)
            : "";
        identity.AddClaim(new Claim(AuthenticationConstants.Gender, user.Gender.ToString()));
        identity.AddClaim(new Claim(AuthenticationConstants.Permissions, permissionClaimValue));
        return identity;
    }
}

permissions = await mediator.Send(new GetRolePermissions.Command { UserRoles = user.Roles }); - 抛出一个错误，因为GetRolePermissions.Handler 需要注入IDbConnection，但当前ApplicationOAuthProvider 的autofac 范围是"root"，并且在此范围内没有注册iDbConnection。但它存在于per-request 范围内。

不想将perLifettime 用于IDbConnection，因为我认为dbConnection 在不必要时应该关闭。我想这样做：

using(var scope = AutofacConfig.container.BeginLifiTime("AutofacWebRequest")) 
{
      permissions = await mediator.Send(new GetRolePermissions.Command { UserRoles = user.Roles });
}

但无法使此解决方案发挥作用。而且我不知道如何正确获取容器，现在它是我手动设置的 AutofacConfig 的静态变量。

如何启用将IDbConnection 注入此GetPermissions.Handler？

Answer 1

实际上，InstancePerLifetimeScope() 是您正在寻找的解决方案。您需要做的就是注入 DbConnection factory 来生成拥有的（docs link 1 和 docs link 2）DbConnection 实例，而不是 DbConnection 本身。

// registration

builder.RegisterType<SqlConnection>()
    .As<IDbConnection>()
    .WithParameter(new NamedParameter("connectionString", WebConfigUtils.DefaultConnectionString))
    .InstancePerLifetimeScope();

// usage

public class GetRolePermissions
{
    public class Command: IRequest<List<string>>
    {
        public ICollection<AspNetUserRole> UserRoles { get; set; }
    }

    public class Handler : AsyncRequestHandler<Command, List<string>>
    {
        private Func<Owned<IDbConnection>> _connectionFactory;

        public Handler(Func<Owned<IDbConnection>> connectionFactory)
        {
            _connectionFactory = connectionFactory;
        }

        // not really sure where your consuming code is, so just something off the top of my head
        public DontKnowYourResultType Handle(GetRolePermissions.Command cmd) {
            using (var ownedConnection = _connectionFactory()) {
                // ownedConnection.Value is the DbConnection you want
                // ... do your stuff with that connection
            } // and connection gets destroyed upon leaving "using" scope
        }
    }
}

它确实改变了请求范围的子范围的行为，但我不确定这是否对您的代码有问题 - 试一试，它应该可以正常工作。如果没有，那么你知道在哪里问。 ;)