How a query is executed and headers + request uri are adjusted

AzureSearchContextTests.cs

using Microsoft.OData.Client;
using System.Linq;
using System.Threading.Tasks;
using Xunit;

namespace Biometria.Discovery.OData.Test
{
    public static class Extensions
    {
        private const int DeltaMilliseconds = 100;

        public static void EnqueueTestComplete(this AzureSearchContextTests test)
        {
            test.IsCompleted = true;
        }

        public static void WaitForTestToComplete(this AzureSearchContextTests test)
        {
            while (!test.IsCompleted)
            {
                Sleep(DeltaMilliseconds);
            }
        }

        private static void Sleep(int milliseconds)
        {
            Task.Delay(milliseconds).Wait();
        }
    }

    public class AzureSearchContextTests
    {
        public bool IsCompleted = false;

        [Fact]
        public void When_FindActors_ItShould_ReturnSingle()
        {
            // Arrange
            AzureSearchContext searchable = new AzureSearchContext("https://(service address)/indexes");

            // Act + Assert
            var query = searchable
                .Actors
                // Use!!!! AddQueryOption("api-version", "2021-04-30-Preview")
                .Where(entity => entity.Identitet == "00043-00000") as DataServiceQuery<Actor>;

            query.BeginExecute(
                (callback) =>
                {
                    var howMany = query.EndExecute(callback).Count();
                    Assert.Equal(1, howMany);

                    this.EnqueueTestComplete();
                },
                default!
            );

            this.WaitForTestToComplete();
        }
    }
}

Microsoft.OData.Client.DataServiceQueryException : An error occurred while processing this request.
---- Microsoft.OData.Client.DataServiceClientException : {"error":{"code":"","message":"Invalid or missing api-version query string parameter."}}
-------- Microsoft.OData.ODataErrorException : An error was read from the payload. See the 'Error' property for more details.

var query = searchable .Actors .AddQueryOption("api-version", "2021-04-30-Preview") .Where(entity => entity.Identitet == "00043-00000") as DataServiceQuery<Actor>;

Using AddQueryOption passes along the api-version