Multi-tenant ASP.NET Core 7 - Defensive database context

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Defensive database context

To make sure that data from different tenants doesn't get mixed in multi-tenant application we can add some defensive behaviour to multi-tenant database context to build additional safety net for application developers.

The following demonstrates defensive database context and it uses the following classes:

ITenantProvider - interface for tenant providers,
DummyTenantProvider - tenant provider for demo purposes,
BaseEntity - base class for all entities,
Person - sample entity type for this demo,
CrossTenantUpdateException - exception type for operations that use data from multiple tenants,
SampleDbContext - defensive database context.

The sample below creates new instance of database context, adds two instances of Person entities that belong to different tenants and then saves changes. If cross-tenant operation exception is thrown then tenant ID-s involved to incident are written out.

Click to run the .NET Core Web app.

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
namespace EFDefensive
{
    public interface ITenantProvider
    {
        Guid GetTenantId();
    }
    public class DummyTenantProvider : ITenantProvider
    {
        public static Guid Tenant1Id = Guid.Parse("51aab199-1482-4f0d-8ff1-5ca0e7bc525a");
        public static Guid Tenant2Id = Guid.Parse("ae4e21fa-57cb-4733-b971-fdd14c4c667e");
        public Guid GetTenantId()
        {
            return Tenant1Id;
        }
    }
    public abstract class BaseEntity
    {
        [Key]
        public int Id { get; set; }
        public Guid TenantId { get; set; }
    }
    public class Person : BaseEntity
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
    public class CrossTenantUpdateException : ApplicationException
    {
        public IList<Guid> TenantIds { get; private set; }
        public CrossTenantUpdateException(IList<Guid> tenantIds)
        {
            TenantIds = tenantIds;
        }
    }
    public class SampleDbContext : DbContext
    {

References

Defensive database context for multi-tenant ASP.NET Core applications (Gunnar Peipman)
Implementing tenant providers on ASP.NET Core (Gunnar Peipman)

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Defensive database context

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