Odata [EnableQuery] attribute makes EF Core crash on high requests amount

Start with the OfficeDtoController.GetOfficeDto entry point and the GetOffices method shown in the issue. Reproduce the example request with $count under concurrent load, comparing it with the request without $count. Done means identifying and resolving the concurrent DbContext operation without regressing the OData query behavior.

I use ASP.NET Wen API on NET 5 and the following NuGets:
Microsoft.AspNetCore.OData => 7.5.4
Microsoft.Data.OData => 5.8.4
Microsoft.OData.Core => 7.8.1
Microsoft.EntityFrameworkCore => 5.0.2

(I have tried with Microsoft.AspNetCore.OData 8.0.0-preview3 and the problem is the same)

#23891 - How the problem started. But this is a different problem so I decided to post a new issue.

In my Odata controller I Use [EnableQuery(EnsureStableOrdering = false)]. Stable ordering is because of some custom Order by which I need in my code. Example in the mentioned Issue above

The problem however is with the [EnableQuery] attribute in general. When I have this attribute in the controller on high load, which means more than 150 request in a minute at the same endpoint I get a lot of the following exception:

"System.InvalidOperationException","Message":"A second operation was started on this context before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext."

"StackTraceString":" at Microsoft.EntityFrameworkCore.Internal.ConcurrencyDetector.EnterCriticalSection()\r\n at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable1.Enumerator.MoveNext()\r\n at System.Linq.Enumerable.Single[TSource](IEnumerable1 source)","RemoteStackTraceString":null,"RemoteStackIndex":0,"ExceptionMethod":null,"HResult":-2146233079,"Source":"Microsoft.EntityFrameworkCore"

I have used testing tool which send that kind of request to my endpoind (Result is around 240 requests in a minute with 1s delay between each) and most of the requests succeed, like maybe around 85% - 90% of them, however the failed requests get the exception above.

I needed some time to figure out what is happening, but when I remove the [EnableQuery] attribute everything was fine. No exception on any level of requests amount.

Here some code:

	public class OfficeDtoController : ODataController
	{
		private readonly IOfficesService _officesService;
		public OfficeDtoController(IOfficesService officesService)
		{
			_officesService = officesService;
		}

		[HttpGet]
		[EnableQuery(EnsureStableOrdering = false)]
		public IActionResult GetOfficeDto(ODataQueryOptions<OfficeDto> queryOptions, Guid? id = null, string sortColumn = "", string sortOrder = "", int? top = null, int? skip = null)
		{
			IQueryable<OfficeDto> officeDto = _officesService.GetOffices(id, sortColumn, sortOrder, top, skip);
			return Ok(officeDto);
		}

And the GetOffices method:

public IQueryable<OfficeDto> GetOffices(Guid? id, string sortColumn, string sortOrder, int? top, int? skip)
{
	IQueryable<Office> query = dbSet;
	query = query
	.Where(z => !z.Deleted);

	var list = query.Select(x =>
		new OfficeDto()
		{
			Id = x.Id,
			ZipCode = x.ZipCode,
			Active = x..Active,
			Employees = x.XrefOfficesEmployees
				.OrderBy(y => y.Order)
				.Select(y => new IdAndName()
				{
					Value = y.EmployeeId,
					Text = y.Employee.FirstName + " " + y.Employee.LastName,
    				Order = y.Order
    			})
    		});
    
	switch (sortColumn)
	{
		case "employees":
			if (sortOrder == "desc")
			{
				officeDto = officeDto.OrderByDescending(b => b.Employees.Select(a => a.Text).FirstOrDefault( ));
    		}
    		else
    		{
    			officeDto = officeDto.OrderBy(b => b.Employees.Select(a => a.Text).FirstOrDefault( ));
    		}
	}
		
	return list;
}

Here is the example URL:

api/OfficeDto?$count=true&$top=20&$skip=0&$select=id,zipcode,employees&$filter=(active eq true)

The exception I get assumes there is some wrong async/await usage, but as it can be seen this is Odata GET request and I do not use async/await anywhere. Maybe there is problem in the communication between EF Core and Odata.

EDIT:

I have found out that without $count it works fine. $Count makes second query to the DB apart from the $Select so I guess this is the problem. Any toughts?