Introduction

ASP.NET Boilerplate provides an IAbpSession interface to obtain the current user and tenant without using ASP.NET's Session. IAbpSession is also fully integrated and used by other structures in ASP.NET Boilerplate such as the setting and authorization systems.

Injecting Session

IAbpSession is generally property injected to needed classes unless it's not possible to work without session information. If we use property injection, we can use NullAbpSession.Instance as a default value, as shown below:

public class MyClass : ITransientDependency
{
    public IAbpSession AbpSession { get; set; }

    public MyClass()
    {
        AbpSession = NullAbpSession.Instance;
    }

    public void MyMethod()
    {
        var currentUserId = AbpSession.UserId;
        //...
    }
}

Since authentication/authorization is an application layer task, it's advisable to use the IAbpSession in the application layer and upper layers. This is not generally done in the domain layer. ApplicationService, AbpController, AbpApiController and some other base classes have AbpSession already injected, so you can, for instance, directly use the AbpSession property in an application service method.

Session Properties

AbpSession defines a few key properties:

• UserId: Id of the current user or null if there is no current user. It can not be null if the calling code is authorized.
• TenantId: Id of the current tenant or null if there is no current tenant (in case of user has not logged in or he is a host user).
• ImpersonatorUserId: Id of the impersonator user, if the current session is impersonated by another user. It's null if this is not an impersonated login.
• ImpersonatorTenantId: Id of the impersonator user's tenant, if the current session is impersonated by another user. It's null if this is not an impersonated login.
• MultiTenancySide: It may be Host or Tenant.

UserId and TenantId are nullable. There are also the non-nullable GetUserId() and GetTenantId() methods. If you're sure there is a current user, you can call GetUserId(). If the current user is null, this method throws an exception. GetTenantId() also works in this way.

Impersonator properties are not as common as other properties and are generally used for audit logging purposes.

ClaimsAbpSession

ClaimsAbpSession is the default implementation of the IAbpSession interface. It gets session properties (except MultiTenancySide, it's calculated) from the claims of the current user's principal. For a cookie-based form authentication, it gets the values from cookies. Thus, it's fully integrated in to ASP.NET's authentication mechanism.

Overriding Current Session Values

In some specific cases, you may need to change/override session values for a limited scope. In such cases, you can use the IAbpSession.Use method as shown below:

public class MyService
{
    private readonly IAbpSession _session;

    public MyService(IAbpSession session)
    {
        _session = session;
    }

    public void Test()
    {
        using (_session.Use(42, null))
        {
            var tenantId = _session.TenantId; //42
            var userId = _session.UserId; //null
        }
    }
}

The Use method returns an IDisposable and it must be disposed. Once the return value is disposed, Session values are automatically restored the to previous values.

If you are using this method in a UniOfWork scope, you may need to call SaveChanges method of the current unit of work in the using statement which wraps _session.Use, otherwise IDisposable object might be disposed before the current unit of work completes and you may get a different value for the UserId and TenantId you intend to use.

public class MyService
{
    private readonly IAbpSession _session;

    public MyService(IAbpSession session)
    {
        _session = session;
    }

    [UnitOfWork()]
    public void Test()
    {
        using (_session.Use(42, null))
        {
            var tenantId = _session.TenantId; //42
            var userId = _session.UserId; //null
            CurrentUnitOfWork.SaveChanges();
        }
    }
}

Warning!

Always use the Use method in a using block as shown above. Otherwise, you may get unexpected session values. You can have nested Use blocks and they will work as you expect.

User Identifier

You can use .ToUserIdentifier() extension method to create a UserIdentifier object from IAbpSession. Since UserIdentifier is used in a lot of APIs, this will simplify the creation of a UserIdentifier object for the current user.