XAF: Multi-Tenancy

Overview

XAF (v24.2+) built-in multi-tenancy for SaaS apps. One deployed instance serves multiple independent organizations (tenants) with strict database isolation (separate DB per tenant).

Key characteristics:

• Blazor Server (ASP.NET Core) — primary supported platform
• Two operating modes: Host UI (tenant management) and Tenant UI (tenant data)
• Tenant connection strings stored in the host database
• Built-in tenant resolver infrastructure

Approaches

Setup (Blazor / v24.2+)

dotnet add package DevExpress.ExpressApp.MultiTenancy

// Program.cs
builder.Services.AddXaf(builder.Configuration, b => {
    b.UseApplication<MyBlazorApplication>();

    b.AddObjectSpaceProviders(providers => {
        providers.UseEntityFramework(ef => {
            ef.DefaultDatabaseConnection("HostConnection", p => p
                .UseDbContext<HostDbContext>());
        });
    });

    b.Security
        .UseIntegratedMode(options => {
            options.RoleType = typeof(PermissionPolicyRole);
            options.UserType = typeof(ApplicationUser);
        })
        .AddPasswordAuthentication();

    b.AddMultiTenancy()
        .WithTenantResolver<TenantByEmailResolver>(); // {User}@{Tenant}
});

Built-in Tenant Resolvers

Custom Tenant Resolver

using DevExpress.ExpressApp.MultiTenancy;

public class TenantBySubdomainResolver : ITenantResolver {
    readonly IHttpContextAccessor _httpContext;

    public TenantBySubdomainResolver(IHttpContextAccessor httpContext) {
        _httpContext = httpContext;
    }

    public Task<string?> GetTenantNameAsync(string? loginName) {
        var host = _httpContext.HttpContext?.Request.Host.Host ?? "";
        var subdomain = host.Split('.').FirstOrDefault();
        return Task.FromResult<string?>(subdomain);
    }
}

// Register:
b.AddMultiTenancy().WithTenantResolver<TenantBySubdomainResolver>();

ITenantProvider Interface

public interface ITenantProvider {
    Guid? TenantId { get; }        // null in Host UI or not logged in
    string? TenantName { get; }    // null in Host UI or not logged in
    object? TenantObject { get; }  // the Tenant persistent object
}

Getting the Current Tenant

From ObjectSpace:

var tenantProvider = objectSpace.ServiceProvider.GetService<ITenantProvider>();
Guid? tenantId     = tenantProvider?.TenantId;
string? tenantName = tenantProvider?.TenantName;

In Controllers via DI:

public class TenantAwareController : ViewController {
    ITenantProvider _tenantProvider;

    [ActivatorUtilitiesConstructor]
    public TenantAwareController(IServiceProvider serviceProvider) : base() {
        _tenantProvider = serviceProvider.GetRequiredService<ITenantProvider>();
    }

    protected override void OnActivated() {
        base.OnActivated();
        var tenantName = _tenantProvider.TenantName;
        // null → Host UI context
    }
}

Tenant-Aware Connection Strings

Each tenant's connection string is stored as a property of the Tenant object in the host DB. XAF uses IConnectionStringProvider to route requests to the correct tenant DB automatically.

// XAF handles routing automatically. Programmatic access if needed:
var connectionStringProvider = serviceProvider.GetService<IConnectionStringProvider>();
string? connStr = connectionStringProvider?.GetConnectionString();

Custom Tenant Class

public class CustomTenant : Tenant {
    public virtual string? LogoUrl { get; set; }
    public virtual string? PrimaryColor { get; set; }
    public virtual int MaxUsers { get; set; }
}

// Register:
b.AddMultiTenancy()
    .WithCustomTenantType<CustomTenant>()
    .WithTenantResolver<TenantByEmailResolver>();

Access:

var tenant = tenantProvider.TenantObject as CustomTenant;
string? logoUrl = tenant?.LogoUrl;

Data Isolation

// In Tenant UI: queries ONLY the current tenant's database — automatic
var orders = objectSpace.GetObjects<Order>();

// Guard for type availability in current context
if (objectSpace.CanInstantiate(typeof(Order))) {
    // safe in this context
}

No built-in cross-tenant query. For aggregated data across tenants, implement outside XAF's ObjectSpace.

User-Tenant Association

• Host DB: super admin accounts, tenant list, shared objects
• Tenant DB: tenant-specific users, roles, permissions, business data

// Create tenant user (run in tenant's ObjectSpace context)
var tenantUser = objectSpace.CreateObject<ApplicationUser>();
tenantUser.UserName = "newuser";
tenantUser.SetPassword("SecurePassword1!");
tenantUser.Roles.Add(defaultRole);
objectSpace.CommitChanges();

Admin Roles

// Host Updater.cs
var superAdminRole = objectSpace.CreateObject<PermissionPolicyRole>();
superAdminRole.Name = "SuperAdministrators";
superAdminRole.IsAdministrative = true;

// Tenant Updater.cs (runs per-tenant DB)
var tenantAdminRole = objectSpace.CreateObject<PermissionPolicyRole>();
tenantAdminRole.Name = "TenantAdministrators";
tenantAdminRole.IsAdministrative = true;

Modules in Multi-Tenant Apps

Modules that register persistent types cannot operate in Host UI mode.

Common Pitfalls

// WRONG
services.AddSingleton<IMyService, MyService>(); // holds tenant-specific state

// CORRECT
services.AddScoped<IMyService, MyService>();

// CORRECT: per-tenant cache keys
string cacheKey = $"{tenantProvider.TenantId}:ProductList";
cache.Set(cacheKey, products);

Source Links

• Multi-tenancy: https://docs.devexpress.com/eXpressAppFramework/404436/multitenancy
• Create Multitenant Application: https://docs.devexpress.com/eXpressAppFramework/404436/multitenancy/create-a-multitenant-application
• Multi-Tenant Architecture: https://docs.devexpress.com/eXpressAppFramework/404436/multitenancy/multi-tenant-application-architecture
• Get Current Tenant in Code: https://docs.devexpress.com/eXpressAppFramework/404668/multitenancy/get-the-current-tenant-in-code
• ITenantProvider API: https://docs.devexpress.com/eXpressAppFramework/DevExpress.ExpressApp.MultiTenancy.ITenantProvider