Scope / Context Manager

Definition

The Scope Manager pattern encapsulates a context change in an IDisposable object. The context is modified at scope creation and automatically restored on Dispose(), guaranteeing a return to the previous state even when an exception occurs.

Diagram

sequenceDiagram
    participant A as Application
    participant CT as CurrentTenant
    participant AL as AsyncLocal

    A->>CT: Change(tenantB)
    CT->>AL: Save previous state (tenantA)
    CT->>AL: Write tenantB
    CT-->>A: IDisposable (TenantScope)

    A->>A: Execute in tenantB context

    A->>CT: Dispose()
    CT->>AL: Restore tenantA

Implementation in Granit

Scope	File	Managed context
TenantScope	src/Granit.MultiTenancy/CurrentTenant.cs	ICurrentTenant.Change(tenantId) — restores previous tenant
FilterScope	src/Granit.Core/DataFiltering/DataFilter.cs	IDataFilter.Disable<T>() — re-enables the filter
Wolverine behaviors	src/Granit.Wolverine/Behaviors/UserContextBehavior.cs	IWolverineUserContextSetter.Change() — restores user

All scopes use AsyncLocal<T> for thread-safe propagation across async/await boundaries.

Rationale

The C# using pattern guarantees Dispose() even when an exception occurs, eliminating the risk of context leaks (a tenant remaining active after an error).

Usage example

// Temporary tenant change -- automatic restoration
using (currentTenant.Change(adminTenantId))
{
    // All queries in this scope target adminTenantId
    List<AuditLog> logs = await db.AuditLogs.ToListAsync(ct);
} // Previous tenant is automatically restored

// Temporarily disable the soft delete filter
using (dataFilter.Disable<ISoftDeletable>())
{
    // Deleted records are visible
    List<Patient> allPatients = await db.Patients.ToListAsync(ct);
} // Filter is automatically re-enabled