XAF: Backend Web API Service

Overview

XAF Web API Service provides OData v4 REST endpoints for XAF business objects. It can run standalone (no UI) or alongside a Blazor app. All XAF security, validation, and ObjectSpace features work the same way.

Project Setup

NuGet Packages

<PackageReference Include="DevExpress.ExpressApp.WebApi" Version="25.1.*" />
<PackageReference Include="DevExpress.ExpressApp.WebApi.Jwt" Version="25.1.*" />
<PackageReference Include="DevExpress.ExpressApp.WebApi.Swashbuckle" Version="25.1.*" />

Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddXaf(builder.Configuration, b => {
    b.UseApplication<MyWebApiApplication>();

    b.AddObjectSpaceProviders(providers => {
        providers.UseEntityFramework(ef => {
            ef.DefaultDatabaseConnection("Default", p =>
                p.UseDbContext<MyDbContext>());
        });
        providers.AddNonPersistent();
    });

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

    b.AddWebApi(options => {
        options.BusinessObject<Contact>();      // expose specific type
        options.BusinessObject<Order>();
        // or expose all: options.BusinessObjects.AddFromAssembly(typeof(Contact).Assembly);
    });
});

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options => {
        options.TokenValidationParameters = new TokenValidationParameters {
            ValidIssuer = builder.Configuration["Jwt:Issuer"],
            ValidAudience = builder.Configuration["Jwt:Audience"],
            IssuerSigningKey = new SymmetricSecurityKey(
                Encoding.UTF8.GetBytes(builder.Configuration["Jwt:Key"]!))
        };
    });

builder.Services.AddSwaggerGen();

var app = builder.Build();
app.UseXaf();
app.UseAuthentication();
app.UseAuthorization();
app.MapControllers();
app.UseSwagger();
app.UseSwaggerUI();
app.Run();

Controlling Business Object Exposure

// Allow/deny specific CRUD operations
[AllowedAction(Operations.Read)]            // read-only
[AllowedAction(Operations.Create | Operations.Read | Operations.Write)]
public class Contact : BaseObject { ... }

// Exclude property from API response
[IgnoreDataMember]
public virtual string InternalNotes { get; set; }

// Programmatic exposure in Program.cs:
b.AddWebApi(options => {
    options.BusinessObject<Order>()
           .AllowedActions(Operations.Read | Operations.Create);
});

OData Queries

GET collection

GET /api/odata/Contact
GET /api/odata/Contact?$filter=City eq 'Warsaw'
GET /api/odata/Contact?$select=FirstName,LastName,Email
GET /api/odata/Contact?$expand=Department
GET /api/odata/Contact?$orderby=LastName asc,FirstName asc
GET /api/odata/Contact?$top=10&$skip=20&$count=true

GET single object

GET /api/odata/Contact(guid'00000000-0000-0000-0000-000000000001')

POST (create)

POST /api/odata/Contact
Content-Type: application/json
Authorization: Bearer <token>

{ "FirstName": "Jan", "LastName": "Kowalski", "Email": "[email protected]" }

PATCH (update)

PATCH /api/odata/Contact(guid'...')
Content-Type: application/json
Authorization: Bearer <token>

{ "Email": "[email protected]" }

DELETE

DELETE /api/odata/Contact(guid'...')
Authorization: Bearer <token>

OData Filter Operators

Authentication

Get Token

POST /api/Authentication/Authenticate
Content-Type: application/json

{ "userName": "Admin", "password": "" }

Response: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."

Use Token

GET /api/odata/Contact
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...

HttpClient Example (C#)

var httpClient = new HttpClient { BaseAddress = new Uri("https://myapp.com") };

// Get token
var tokenResponse = await httpClient.PostAsJsonAsync(
    "/api/Authentication/Authenticate",
    new { userName = "Admin", password = "" });
var token = await tokenResponse.Content.ReadAsStringAsync();

// Use token
httpClient.DefaultRequestHeaders.Authorization =
    new AuthenticationHeaderValue("Bearer", token.Trim('"'));

// Query data
var contacts = await httpClient.GetFromJsonAsync<ODataResult<Contact>>(
    "/api/odata/Contact?$filter=Active eq true");

Custom Endpoints

Custom OData Action (POST, modifies data)

// In a controller (or XAF business logic class):
[ApiController]
[Route("api/[controller]")]
public class OrderController : ControllerBase {
    private readonly IObjectSpaceFactory _objectSpaceFactory;

    public OrderController(IObjectSpaceFactory objectSpaceFactory) {
        _objectSpaceFactory = objectSpaceFactory;
    }

    [HttpPost("api/odata/Order({key})/ProcessOrder")]
    public IActionResult ProcessOrder([FromRoute] Guid key) {
        using var os = _objectSpaceFactory.CreateObjectSpace(typeof(Order));
        var order = os.GetObjectByKey<Order>(key);
        if (order == null) return NotFound();
        order.Status = OrderStatus.Processed;
        os.CommitChanges();
        return Ok();
    }
}

Or via XAF's [Action] attribute on a non-persistent class:

[DomainComponent]
public class OrderActions {
    [Action(Caption = "ProcessOrder")]
    public void ProcessOrder(Order order, IObjectSpace objectSpace) {
        order.Status = OrderStatus.Processed;
        objectSpace.CommitChanges();
    }
}

Swagger / OpenAPI

Automatically available at /swagger when configured. All OData endpoints are documented.

Security Integration

All OData endpoints automatically apply XAF security:

• Permissions filter which records are returned (object-level security)
• Member-level permissions hide specific properties
• DenyAllByDefault → explicit grants required for API access

No additional configuration needed — security works transparently via ObjectSpace.

Pagination Pattern

GET /api/odata/Contact?$top=10&$skip=0&$count=true

Response includes @odata.count with total count. Client paginates by incrementing $skip.

v24.2 vs v25.1 Differences

Source Links

• Backend Web API Service: https://docs.devexpress.com/eXpressAppFramework/403394/backend-web-api-service
• Get Started with Web API: https://docs.devexpress.com/eXpressAppFramework/403394/backend-web-api-service/get-started-with-the-web-api-service
• Use OData to Query Data: https://docs.devexpress.com/eXpressAppFramework/403551/backend-web-api-service/use-odata-to-query-data
• Authentication in Web API: https://docs.devexpress.com/eXpressAppFramework/403716/backend-web-api-service/authentication-in-web-api-projects
• Custom Endpoints: https://docs.devexpress.com/eXpressAppFramework/403715/backend-web-api-service/custom-endpoint