What is the best way to use in memory data in Asp.net Web API project for demo

Question

I am building Asp.net Web API demo project, i don't want to use any data provider, neither entity framework nor Ado.net.

I build the Repository,

public class ProductRepo : IProductRepo
{
    private List<Product> products = new List<Product>();
    private int _nextId = 1;

    public ExternalProductDataRepo()
    {
        products.Add(new Product {Id=1, Name = "Toyata", Category = "Car", Price = 1.3M });
        products.Add(new Product {Id=2,  Name = "Ford", Category = "Car", Price = 3.75M });
        products.Add(new Product {Id=3, Name = "Hammer", Category = "Hardware", Price = 16.99M });
    }

    public IEnumerable<Product> GetAll()
    {
        return products;
    }

    public Product Get(int id)
    {
        return products.Find(p => p.Id == id);
    }

    public Product Add(Product item)
    {
        if (item == null)
        {
            throw new ArgumentNullException("item");
        }
        item.Id = _nextId++;
        products.Add(item);
        return item;
    }

    public void Remove(int id)
    {
        products.RemoveAll(p => p.Id == id);
    }

    public bool Update(Product item)
    {
        if (item == null)
        {
            throw new ArgumentNullException("item");
        }
        int index = products.FindIndex(p => p.Id == item.Id);
        if (index == -1)
        {
            return false;
        }
        products.RemoveAt(index);
        products.Add(item);
        return true;
    }
}

But, in every app hit, a new instance of ProductRepo class is created, so even though i save the data, it never persisted.

Also, i have the option of using, System.Web.Cache, to hold the products list in Cache, but it is for a different purpose and for a limited period of time, also it makes isolated unit testing difficult. So, what is the suggestion to build the successive demo project with products CRUD operation?

Make List<Product> products static. It will work while application running and serves demo purposes. — Fabio
– Fabio, Commented Dec 14, 2016 at 6:14

PartlyCloudy · Accepted Answer · 2016-12-14 07:16:12Z

1

You want your repository to be a singleton. There are multiple ways to achieve this, but if this demo code is going to become operational in some way, I would suggest integrating a dependency injection provider into your code. For example, you could use unity.

You set up your repository as a singleton in the container.
You controllers will get passed the IProductRepo interface. This means that if you decide to change the implementation to an actual data provider, your code will not need to change - you will simply change the registration in your DI container.

Here are some resources to help you get started if you want to implement this path:

Install Unity.WebAPI nuget package. See http://www.devtrends.co.uk/blog/introducing-the-unity.webapi-nuget-package

In your App_Start folder, add a static UnityConfig class:

public static class UnityConfig
{
    public static void RegisterComponents()
    {
        var container = new UnityContainer();

        container.RegisterType<<IProductRepo>,<ProductRepo>> (new ContainerControlledLifetimeManager());
        container.Resolve<IProductRepo>();

        GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);
    }
}

In your Global.asax file, add the following line: UnityConfig.RegisterComponents();
Now in the constructor of your controller, just pass a member of type IProductRepo. This will be initialized for you by Unity, and will be the same instance every app hit since it is created once by Unity.

answered Dec 14, 2016 at 7:16

PartlyCloudy

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2 Comments

Guillaume Over a year ago

The repository is clearly not thread-safe. You have to be really carefull when you change the lifetime.

artisanbhu Over a year ago

I was also using the Unity as a dependency injection container, but, instead of container.RegisterType<<IProductRepo>,<ProductRepo>> (new ContainerControlledLifetimeManager());, Instead of ContainerControlledLifetimeManager, i was using new HierarchicalLifetimeManager(), that was creating instance all the time, now it is solved, thank you

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