Minimal APIs Cannot Expand Single Entity

[andrew-turrentine]

With minimal APIs, I cannot figure out how to have $expand work properly when the $expand is one a single entity and not a collection.

If I use .FirstOrDefault(...) then I get expected results and a valid entity - $select even works.

However, if I try to use SingleResult<T> with .Where(...) for $expand then I start to get errors related to conversions or the wrapped type not being present in the model

The given model does not contain the type 'Microsoft.AspNetCore.OData.Results.SingleResult1[[Turpy.Nexus.Data.Entities.Organization, Turpy.Nexus.Data, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]'. (Parameter 'elementClrType')

Can someone give me an example of how to accomplish this or check if this is a bug? I can have it return a collection of 1 item but that is not very clean or performant.

[xuzhg]

@andrew-turrentine Would you please share use a simple repro or your minimal endpoints?

[andrew-turrentine]

Hi, I have tried a few things:

With the following endpoint mapping:

group.MapGet("/{id:guid}", GetByIdAsync<TEntity>)
    .WithODataResult()
    .WithODataModel(edmModel)
    .WithName($"Get{typeof(TEntity).Name}")
    .WithSummary($"Get {typeof(TEntity).Name} by ID");

This gets an exception:

  private static object GetByIdAsync<TEntity>(NexusDbContext db,
      Guid id,
      ODataQueryOptions<TEntity> queryOptions,
      CancellationToken cancellationToken)
      where TEntity : Entity
  {
      var entity = SingleResult.Create(db.Set<TEntity>().Where(e => e.Id == id));

      return queryOptions.ApplyTo(entity, new ODataQuerySettings());
  }

This and other IResult return values don't work with the OData metadata responses and some query options.

private static IResult GetByIdAsync<TEntity>(NexusDbContext db,
    Guid id,
    ODataQueryOptions<TEntity> queryOptions,
    CancellationToken cancellationToken)
    where TEntity : Entity
{
    var entity = SingleResult.Create(db.Set<TEntity>().Where(e => e.Id == id));

    if (entity is null)
        return Results.NotFound();

    return Results.Ok(queryOptions.ApplyTo(entity, new ODataQuerySettings()));
}

Other combinations with SingleResult but a generic or object as return type often get Object of type 'Microsoft.AspNetCore.OData.Results.SingleResult`1[MyEntityType]' cannot be converted to type 'MyEntityType'.

I also tried similar with

group.MapGet("/{id:guid}", GetByIdAsync<TEntity>)
    .AddODataQueryEndpointFilter()
    .WithODataResult()
    .WithODataModel(edmModel)
    .WithName($"Get{typeof(TEntity).Name}")
    .WithSummary($"Get {typeof(TEntity).Name} by ID");

And then removing the queryOptions part of the method.

If I use FirstOrDefault then everything works as expected - aside from Expand not working (which makes sense to me).

Expand is working everywhere that I am returning a collection as expected.