实体框架核心-非线程安全- ServiceLifetime.Transient

Question

看来，我的数据库上下文并不是线程安全的、瞬态的，甚至是我指定的：

ServiceLifetime.Transient 

在数据库的启动配置中。

Startup.cs

services.AddEntityFrameworkSqlServer().AddDbContext<DatabaseContext>((serviceProvider, options) => options.UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking).UseSqlServer(connectionString).UseInternalServiceProvider(serviceProvider), ServiceLifetime.Transient);

Api

[HttpPost("GetOrganisations")] //Yes post, dont harass me :)
public async Task<IActionResult> GetOrganisations([FromBody] GetOrganisationsModel model)
{
    Task<IEnumerable<OrganisationModel>> organisations = _organisationService.GetOrganisations(model?.Id, model?.StatusIds);

    Task<int> organisationTotalCount = _organisationService.GetOrganisationCount();

    await Task.WhenAll(organisations, organisationTotalCount);

    return Ok(new OrganisationViewModel
    {
        Organisations = await organisations,
        OrganisationTotalCount = await organisationTotalCount
    });
}

回购

public class OrganisationRepository : IOrganisationRepository
{
    private readonly DatabaseContext _database;

    public OrganisationRepository(DatabaseContext database)
    {
        _database = database;
    }

    public async Task<List<OrganisationEntity>> GetOrganisations(int? organisationId, List<int> statusIds)
    {
        IQueryable<OrganisationEntity> organisations = Database.Organisation.Include(o => o.Status).OrderByDescending(d => d.Created).AsQueryable();

        if (organisationId != null)
        {
            organisations = organisations.Where(o => o.Id == organisationId);
        }

        if (statusIds != null && statusIds.Count > 0)
        {
            organisations = organisations.Where(o => statusIds.Contains(o.StatusId));
        }

        return await organisations.ToListAsync();
    }

    public async Task<int> GetOrganisationCount()
    {
        return await Database.Organisation.CountAsync();
    }
}

异常

System.InvalidOperationException:连接没有关闭。连接的当前状态是连接。

这里的问题是，我调用GetOrganisations()和GetOrganisationCount()异步，并且由于某种原因(我认为)，对两个调用(不同的线程)使用相同的数据库连接。我认为通过增加选项：

ServiceLifetime.Transient 

它可以解决我的问题(因为默认范围是限定的)，但不..

但是，如果我添加使用语句。

public async Task<List<OrganisationEntity>> GetOrganisations(int? organisationId, List<int> statusIds)
{
    var optionsBuilder = new DbContextOptionsBuilder<DatabaseContext>();
    optionsBuilder.UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking)
        .UseSqlServer(
            "Data Source=.;Initial Catalog=MYDATABASE;Integrated Security=True;Connect Timeout=30;");

    using (var db = new DatabaseContext(optionsBuilder.Options, null))
    {
        IQueryable<OrganisationEntity> organisations =
            db.Organisation.Include(o => o.Status).OrderByDescending(d => d.Created).AsQueryable();

        if (organisationId != null)
        {
            organisations = organisations.Where(o => o.Id == organisationId);
        }

        if (statusIds != null && statusIds.Count > 0)
        {
            organisations = organisations.Where(o => statusIds.Contains(o.StatusId));
        }

        return await organisations.ToListAsync();
    }
}

public async Task<int> GetOrganisationCount()
{
    var optionsBuilder = new DbContextOptionsBuilder<DatabaseContext>();
    optionsBuilder.UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking)
        .UseSqlServer(
            "Data Source=.;Initial Catalog=MYDATABASE;Integrated Security=True;Connect Timeout=30;");

    using (var db = new DatabaseContext(optionsBuilder.Options, null))
    {
        return await db.Organisation.CountAsync();
    }
}

一切正常！

为什么依赖注入不能正常工作？

，我是不是完全搞错了？如果我需要临时上下文，是否被迫在所有任务中使用use语句？

ServiceLifetime.Transient窃听了？！

编辑：

Stacktrade，(一些信息蒙面)

在System.Data.ProviderBase.DbConnectionClosedConnecting.TryOpenConnection(DbConnection outerConnection，DbConnectionFactory connectionFactory，TaskCompletionSource1 retry, DbConnectionOptions userOptions)\r\n \r\n在System.Data.SqlClient.SqlConnection.OpenAsync(CancellationToken cancellationToken)\r\n--从抛出异常的前一个位置开始的堆栈跟踪的结束--\\r\n在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n (在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task任务中)\r\n在堆栈跟踪的Microsoft.EntityFrameworkCore.Storage.RelationalConnection.d__31.MoveNext()\r\n---末端，从抛出异常的以前位置开始 (在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task任务中)\r\n在堆栈跟踪的Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable.AsyncEnumerator.d__9.MoveNext()\r\n---末端，从抛出异常的以前位置开始 (在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task任务中)\r\n在Microsoft.EntityFrameworkCore.Storage.Internal.SqlServerExecutionStrategy.d__62.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable.AsyncEnumerator.<MoveNext>d__8.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n 1.MoveNext()\r\n--在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n中抛出异常的前一个位置的堆栈跟踪的结束-\r\n (在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task任务中)\r\n在Microsoft.EntityFrameworkCore.Query.Internal.TaskResultAsyncEnumerable1.Enumerator.<MoveNext>d__3.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n 从抛出异常的前一个位置开始的堆栈跟踪的at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor1.EnumeratorExceptionInterceptor.d__5.MoveNext()\r\n---结束-\r\n在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n (在System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task任务中)\r\n在System.Runtime.CompilerServices.TaskAwaiter1.GetResult()\r\n at XXXXXXX.Data.Repositories.Organisation.OrganisationRepository.<GetOrganisationCount>d__8.MoveNext() in C:\\Users\\XXXXXXX\\Documents\\Visual Studio 2017\\Projects\\XXXXXXX\\XXXXXXX.Data\\Repositories\\Organisation\\OrganisationRepository.cs:line 65\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n C中XXXXXXX.Api.Services.Organisation.OrganisationService.d__4.MoveNext()的at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter1.1.GetResult()\r\n：\User\XXXXXXX\Documents\Visual 2017\Projects\XXXXXXX\XXXXXXX.Api\Services\Organisation\OrganisationService.cs:line 31\r\n--从抛出异常的前一个位置开始的堆栈跟踪的结束--\\r\n位于System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n \r\n in System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n at XXXXXXX.Api.Controllers.Administration.OrganisationController.d__5.MoveNext() in C:\Users\XXXXXXX\Documents\Visual 2017\Projects\XXXXXXX\XXXXXXX.Api\Controllers\Administration\OrganisationController.cs:line 51“

Answer 1

ServiceLifetime.Transient窃听了？！

这不是窃听器。正如我们所知道的，DbContext并不是线程安全的，这两个方法调用使用相同的OrganisationService实例，这些实例本身是使用DatabaseContext的相同实例创建的。

Task<IEnumerable<OrganisationModel>> organisations = 
    _organisationService.GetOrganisations(model?.Id, model?.StatusIds);

Task<int> organisationTotalCount = _organisationService.GetOrganisationCount();

它是线程交换环境下实体框架DbContext的一个限制。因此，我们采用以下传统方法-

[HttpPost("GetOrganisations")]
public async Task<IActionResult> GetOrganisations([FromBody] GetOrganisationsModel model)
{
    var organisations = 
        await  _organisationService.GetOrganisations(model?.Id, model?.StatusIds);

    var organisationTotalCount = await _organisationService.GetOrganisationCount();

    return Ok(new OrganisationViewModel
    {
        Organisations = organisations,
        OrganisationTotalCount = organisationTotalCount
    });
}

newing在存储库中的缺点是它们变得紧密耦合，您不能像这那样对存储库进行单元测试。如果在特定场景中必须在Task.WhenAll与单元测试之间进行选择，那么我将选择Unit。

如果您看到自己经常使用Task.WhenAll，您可能需要查看可以与EF一起使用的Dapper ORM。

Answer 2

还请注意，在Microsoft依赖项注入中，在作用域结束之前，暂存服务不会被释放。

有一种简单的方法，就是使用WeakReference代替TService作为临时的。然后，WeakReference的用户可以负责处理。