> ## Documentation Index
> Fetch the complete documentation index at: https://easyaf.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# In-Memory Data Provider

> Build OData services with all-in-memory resources

## In-Memory Data Provider

RESTier supports building an OData service with **all-in-memory** resources. However currently RESTier
has not provided a dedicated in-memory provider module so users have to write some service code to bootstrap
the initial model with EDM types themselves. There is a sample service with in-memory provider [here](https://github.com/OData/RESTier/tree/apidev/test/ODataEndToEndTests/Microsoft.OData.Service.Sample.TrippinInMemory).
This subsection mainly talks about how such a service is created.

First please create an **Empty ASP.NET Web API** project following the instructions in [Section 1.2](http://odata.github.io/RESTier/#01-02-Bootstrap). Stop **BEFORE** the **Generate the model classes** part.

### Create the Api class

Create a simple data type `Person` with some properties and "fabricate" some fake data. Then add the first entity set `People` to the `Api` class:

```csharp theme={"dark"}
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Web.OData.Builder;
using Microsoft.OData.Edm;
using Microsoft.Restier.Core;
using Microsoft.Restier.Core.Model;

namespace Microsoft.OData.Service.Sample.TrippinInMemory
{
    public class TrippinApi : ApiBase
    {
        private static readonly List<Person> people = new List<Person>
        {
            ...
        };

        public IQueryable<Person> People
        {
            get { return people.AsQueryable(); }
        }
    }
}
```

### Create an initial model

Since the RESTier convention will not produce any EDM type, an initial model with at least the `Person` type needs to be created by service. Here the `ODataConventionModelBuilder` from OData Web API is used for quick model building.
Any model building methods supported by Web API OData can be used here, refer to **[Web API OData Model builder](http://odata.github.io/WebApi/#02-01-model-builder-abstract)** document for more information.

```csharp theme={"dark"}
namespace Microsoft.OData.Service.Sample.TrippinInMemory
{
    public class TrippinApi : ApiBase
    {
        protected override IServiceCollection ConfigureApi(IServiceCollection services)
        {
            services.AddService<IModelBuilder>(new ModelBuilder());
            return base.ConfigureApi(services);
        }

        private class ModelBuilder : IModelBuilder
        {
            public Task<IEdmModel> GetModelAsync(InvocationContext context, CancellationToken cancellationToken)
            {
                var builder = new ODataConventionModelBuilder();
                builder.EntityType<Person>();
                return Task.FromResult(builder.GetEdmModel());
            }
        }
    }
}
```

### Configure the OData endpoint

Replace the `WebApiConfig` class with the following code. No need to create a custom controller if users don't have attribute routing.

```csharp theme={"dark"}
using System.Web.Http;
using Microsoft.Restier.Publisher.OData.Batch;

namespace Microsoft.OData.Service.Sample.TrippinInMemory
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            config.MapRestierRoute<TrippinApi>(
                "TrippinApi",
                "api/Trippin",
                new RestierBatchHandler(GlobalConfiguration.DefaultServer)).Wait();
        }
    }
}
```