An ASP.NET Core Web API CRUD Service

When building a Web API service, it is convenient to separate your Controller's code from the data access logic. Don't deal with SQL, DB connections, etc. each time you need to extend your API, but use the database-independent object-oriented approach to retrieve data with sorting, filtering and complex data shaping.

The persistent object JSON serialization feature makes it easy to use XPO as a Data Access layer in an ASP.NET Core Web API service. You no longer need to manually format JSON responses or make a POCO copy of each persistent class. This tutorial demonstrates how to enable this feature and implement a few Controllers.

You may also be interested in the following examples:

• How to Implement OData v4 Service with XPO (.NET Core)
• How to Implement OData v4 Service with XPO (.NET Framework)

Prerequisites

Visual Studio 2019 with the following workloads:

• ASP.NET and web development
• .NET Core cross-platform development
• .NET Core 3.1 SDK or later

Create the project

Use the following steps to create a project or refer to the original tutorial in the Microsoft documentation.

• From the File menu, select New > Project.
• Select the ASP.NET Core Web Application template and click Next. Fill in the Name field and click the Create button.
• In the Create a new ASP.NET Core web application dialog, choose the ASP.NET Core version. Select the API template and click Create.

Configure XPO

• Install DevExpress.XPO Nuget package.
  Install-Package DevExpress.Xpo

• Use the ORM Data Model Wizard to create the data model or generate it from the existing database.

• Add the connection string to the appsettings.json file.

  "ConnectionStrings": {
     "SQLite": "XpoProvider=SQLite;Data Source=demo.db",
     "MSSqlServer": "XpoProvider=MSSqlServer;data source=(local);user id=sa;password=;initial catalog=XpoASPNETCoreDemo;Persist Security Info=true"
  }

• Open the Startup.cs file and register the UnitOfWork Service as described in ASP.NET Core Dependency Injection in XPO.

  public void ConfigureServices(IServiceCollection services) {
           services.AddControllersWithViews();
           services.AddCors();
           services.AddXpoDefaultUnitOfWork(true, (DataLayerOptionsBuilder options) =>
               options.UseConnectionString(Configuration.GetConnectionString("MSSqlServer"))
                //.UseAutoCreationOption(AutoCreateOption.DatabaseAndSchema) // debug only
               .UseEntityTypes(ConnectionHelper.GetPersistentTypes()));
           //...
  }

• In the Startup.cs also register custom JSON converter and Metadata provider Services.

          //...
          services.AddHttpContextAccessor();
          services.ConfigureOptions<ConfigureJsonOptions>();
          services.AddSingleton(typeof(IModelMetadataProvider), typeof(XpoMetadataProvider));
          //...

• Add the JsonConverters.cs file to your project.

Create a Controller

• Declare a local variable to store the UnitOfWork instance passed as a constructor parameter.

  [ApiController]
  [Route("api/[controller]")]
  public class CustomersController : ControllerBase {
     private UnitOfWork uow;
     public CustomersController(UnitOfWork uow) {
        this.uow = uow;
     }

• GET methods implementation is simple and straightforward. Load object(s) from the database and return the result.

  [HttpGet]
  public IEnumerable Get() {
     return uow.Query<Customer>();
  } 
  [HttpGet("{id}")]
  public Customer Get(int id) {
    return uow.GetObjectByKey<Customer>(id);
  }

• The POST method creates a new persistent object and saves it to the database.

  [HttpPost]
  public IActionResult Post([FromBody] Customer customer) {
     try {
        uow.CommitChanges();
        return NoContent();
     } catch(Exception exception) {
        return BadRequest(exception);
     }
  } 

• The PUT and DELETE methods do not require any special remarks.

  [HttpPut("{id}")]
  public IActionResult Put(int id, [FromBody] Customer customer) {
     if(id != customer.Oid)
        return NotFound();
     try {
        uow.CommitChanges();
        return NoContent();
     } catch(Exception exception) {
        return BadRequest(exception);
     }
  }
  [HttpDelete("{id}")]
  public IActionResult Delete(int id) {
     try {
        Customer customer = uow.GetObjectByKey<Customer>(id);
        uow.Delete(customer);
        uow.CommitChanges();
        return NoContent();
     } catch(Exception exception) {
        return BadRequest(exception);
     }
  }