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

Approach	Isolation	Notes
Separate DB per tenant	Full	Default XAF approach; maximum isolation
Shared DB with discriminator	Partial	Not natively supported — must implement manually
Hybrid	Mixed	Shared config in host DB; operational data in tenant DBs

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

Resolver	Login Pattern	Example
`TenantByEmailResolver`	`{User}@{Tenant}`	`john@acme` → tenant = "acme"
`TenantByUserNameResolver`	Custom regex	`acme//john` → tenant = "acme"

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

Role	DB	Responsibilities
Super Administrator	Host DB	Creates/deletes tenants, host config
Tenant Administrator	Tenant DB	Users, roles, permissions within tenant
Tenant User	Tenant DB	Normal end-user access

// 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

Module	Host UI	Tenant UI
Business data modules	No	Yes
Dashboards	No	Yes
File Attachments	No	Yes
Reports V2	No	Yes
Scheduler	No	Yes
Security module	Yes	Yes

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

Common Pitfalls

Pitfall	Solution
Singleton services holding tenant state	Use scoped services; never store tenant data in singletons
Same connection string for host and tenant	Always different connection strings — framework enforces this
Shared in-memory cache leaking across tenants	Use per-tenant cache keys: `$"{tenantId}:{cacheKey}"`
Querying business types in Host UI	Guard with `objectSpace.CanInstantiate(typeof(T))`
Missing DB migration per tenant	Run migration per tenant DB via XAF's updater infrastructure

// 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

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