OData C# (How It Works For Developers)

Let's create a simple OData model class in an ASP.NET Core application. In the following code, the below class will expose a list of services that can be queried using the OData syntax.

public class Service
{
    public int Id { get; set; } 
    public string FirstName { get; set; }
    public decimal Price { get; set; }
}

public class Service
{
    public int Id { get; set; } 
    public string FirstName { get; set; }
    public decimal Price { get; set; }
}

Description of the code

The Service class represents a basic data structure in C# for managing a service. It includes three properties: Id: An integer identifier for the service. FirstName: A string representing the first name associated with the service. Price: A decimal value indicating the price of the service. This class can be used as a building block for creating more complex service-related functionality in .NET development. We may also use collection or navigation properties based on the scenario.

Here's how you can set up an OData controller in an ASP.NET Core application in Visual Studio to expose a list of services via a standardized OData endpoint. The following example demonstrates a basic implementation using a static list of services and enabling OData query functionalities in Web API:

using DemoOData.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.OData.Query;
using Microsoft.AspNetCore.OData.Routing.Controllers;

namespace DemoOData.Controllers
{
    [Route("odata/[controller]")]
    public class ServiceController : ODataController
    {
        private static readonly List<Service> Products = new List<Service>
        {
            new Service { Id = 1, FirstName = "Laptop", Price = 6239.9M },
            new Service { Id = 2, FirstName = "Smartphone", Price = 2585.9M }
        };

        [HttpGet]
        [EnableQuery]
        public IActionResult Get() => Ok(Products);
    }
}

using DemoOData.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.OData.Query;
using Microsoft.AspNetCore.OData.Routing.Controllers;

namespace DemoOData.Controllers
{
    [Route("odata/[controller]")]
    public class ServiceController : ODataController
    {
        private static readonly List<Service> Products = new List<Service>
        {
            new Service { Id = 1, FirstName = "Laptop", Price = 6239.9M },
            new Service { Id = 2, FirstName = "Smartphone", Price = 2585.9M }
        };

        [HttpGet]
        [EnableQuery]
        public IActionResult Get() => Ok(Products);
    }
}

Description of the code

The provided code defines an ODataController named ServiceController in an ASP.NET Core application, enabling querying and manipulating data using the OData protocol. It routes requests to odata/Service and serves a static list of Service objects, including a laptop and a smartphone. The Get method, decorated with [EnableQuery], allows clients to perform OData queries (filtering, sorting, paging) on the Products list, returning the results as an IActionResult for HTTP GET requests.

Register OData Services in the Program.cs

To integrate OData into a .NET 6 application, we need to install and configure the necessary OData packages. This involves defining the OData model, setting up the OData middleware, and configuring services to support OData features such as filtering, ordering, and expansion.

using DemoOData.Models;
using Microsoft.AspNetCore.OData;
using Microsoft.OData.Edm;
using Microsoft.OData.ModelBuilder;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

static IEdmModel GetEdmModel()
{
    ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
    builder.EntitySet<Service>("Services");
    return builder.GetEdmModel();
}

builder.Services.AddControllers()
    .AddOData(options => options
        .AddRouteComponents("odata", GetEdmModel())
        .Select()
        .Filter()
        .OrderBy()
        .SetMaxTop(20)
        .Count()
        .Expand()
    );

using DemoOData.Models;
using Microsoft.AspNetCore.OData;
using Microsoft.OData.Edm;
using Microsoft.OData.ModelBuilder;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

static IEdmModel GetEdmModel()
{
    ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
    builder.EntitySet<Service>("Services");
    return builder.GetEdmModel();
}

builder.Services.AddControllers()
    .AddOData(options => options
        .AddRouteComponents("odata", GetEdmModel())
        .Select()
        .Filter()
        .OrderBy()
        .SetMaxTop(20)
        .Count()
        .Expand()
    );

Description of the code

This code configures OData support in a .NET 6 application. First, it imports necessary namespaces and creates a WebApplicationBuilder instance. The GetEdmModel method defines the OData model using the ODataConventionModelBuilder, which specifies an entity set for Service entities. The AddOData method is then called to configure OData services, including enabling select, filter, order by, count, expand, and setting a maximum top value of 20 for query results. This setup ensures the application can handle OData queries effectively.

The AddOData() method employs the GetEdmModel() method, which retrieves the data model used for querying, forming the foundation of an OData service. This service utilizes an abstract data model known as Entity Data Model (EDM) to define the exposed data. The ODataConventionModelBuilder class generates an EDM through default naming conventions, minimizing code requirements. Alternatively, developers can utilize the ODataModelBuilder class for greater control over the EDM.

Screenshot of the code