ASP.NET Core OData 8.x does not work with Minimal API

[Lonli-Lokli]

Assemblies affected
ASP.NET Core OData 8.x

Describe the bug
OData does not work with Minimal API, ie without Controllers

Reproduce steps

app.MapGet("/WeatherForecast", [EnableQuery] () => Enumerable.Range(1, 5).Select((int index) => new WeatherForecast
    {
        Date = DateTime.Now.AddDays(index),
        TemperatureC = Random.Shared.Next(-20, 55),
        Summary =  new[]  {
            "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
        }
    })
    .ToArray());
app.Run();

Expected behavior
I would like to use OData without Controllers at all

[ElizabethOkerio]

@Lonli-Lokli could you please provide us with more information on any problems you are getting with using the Minimal Api with OData

[Lonli-Lokli]

@ElizabethOkerio Basically I would like to use OData with only Minial Api, without enabling Controllers on MVC (.AddControllers) or writing OData Controllers with EnableQuery.

I want to use OData with pure Minimal API endpoint - specify [EnableQuery] and make it works same as with Controller.

Now it does not work

[TehWardy]

So basically this is the problem ...

        public static void AddApi(this IServiceCollection services)
        {
            _ = services.AddControllers()
                .AddOData(opt =>
                {
                    opt.RouteOptions.EnableQualifiedOperationCall = false;
                    opt.EnableAttributeRouting = true;
                    _ = opt.Expand().Count().Filter().Select().OrderBy().SetMaxTop(1000);
                    opt.AddRouteComponents($"/Odata", new MyEdmModel());
                });
        }

... the setup for odata is dependant on this it seems ...
services.AddControllers() <--
...

Random thought though ...
Have you tried just injecting an ODataOptions in to the get endpoint you're mapping and then using that directly?

In a controller situation it would look like this ...

public class FooController
{
       [HttpGet]
       [EnableQuery]
       public virtual IActionResult Get(ODataQueryOptions<Foo> queryOptions)
           => Ok(queryOptions.ApplyTo(service.GetAll()));
}

I can't see any reason why that couldn't be done in a minimal API sitation unless the above MUST be made in order for some DI thing to be configured.

So this makes your potential solution something like ...

app.MapGet("/WeatherForecast", [EnableQuery] (ODataQueryOptions<WetherData> options) => 
    options.ApplyTo(
        Enumerable.Range(1, 5).Select((int index) => new WeatherForecast
         {
             Date = DateTime.Now.AddDays(index),
             TemperatureC = Random.Shared.Next(-20, 55),
             Summary =  new[]  {
                 "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
             }
         })
     ) .ToArray());
app.Run();

[Lonli-Lokli]

I was able to call AddOdata without AddControllers with Reflection

var odataMethod = typeof(ODataMvcCoreBuilderExtensions).GetMethod("AddODataCore", BindingFlags.NonPublic | BindingFlags.Static);
odataMethod?.Invoke(null, null);

But your approach with ODataQueryOptions will not work as ODataQueryOptions are not registered as service.

As an addition, AttributeRouting or ConventionRouting doesnt make much sense with Minimal Api. The best use case is as I described above - non-edm way with EnableQuery

[TehWardy]

Just took a look at the code ...

    public class ODataQueryOptions<TEntity> : ODataQueryOptions
    {
        public ODataQueryOptions(ODataQueryContext context, HttpRequest request)

... so you're gonna need to do this ...

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

     var edmModel = GetEdmModel();
     builder.Services.AddScoped<ODataQueryOptions<WeatherForcast>>(ctx => 
         new ODataQueryContext(edmModel, typeof(WeatherForecast));   

... OData is dependent on EDM Models it seems at the moment, there's no way to escape that.
this should at least allow you to get the functionality.

[Lonli-Lokli]

Even according to your sample it's clear that ODataQueryOptions cannot be added during application building as they requires HttpRequest. Also

builder.Services.AddScoped<ODataQueryOptions<WeatherForcast>>(ctx => 
         new ODataQueryContext(edmModel, typeof(WeatherForecast));   

will not compile because thi constructor is internal, also ODataQueryContext cannot be casted ODataQueryOptions.
More valid (but still producing incorrect API results) is

var Summaries = new[]
{
    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
};

app.MapGet("/WeatherForecast", (HttpRequest request) =>
    new ODataQueryOptions<WeatherForecast>(new ODataQueryContext(edmModel, typeof(WeatherForecast), null), request)
        .ApplyTo(Enumerable
            .Range(1, 5).Select((int index) => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = Random.Shared.Next(-20, 55),
                Summary = Summaries[new Random().Next(Summaries.Length)]
            })
            .AsQueryable()));

It will cycled data instead of similar code with controllers