Writing to the response body is invalid for responses with status code 204.

[rfcdejong]

Using in .NET Core 3.1

EfCore.GenericBizRunner 4.0.0
EfCore.GenericServices.AspNetCore 4.0.0

The following code

        [HttpGet("{id}", Name = "GetSingleRelation")]
        public async Task<ActionResult<WebApiMessageAndResult<RelationEntity>>> GetSingleAsync(Guid id, [FromServices]ICrudServicesAsync<DataDbContext> service)
        {
            var relation = await service.ReadSingleAsync<RelationEntity>(id);
            return service.Response(relation);
        }

service.Response(null) says

This will return a result value, with the status Message 1. If there are no errors and the result is not null it will return a HTTP 200 response plus a json containing the message from the status and the results object 2. If there are no errors but result is null it will return a HTTP 204 (NoContent) with the status Message 3. If there are errors it returns a HTTP 400 with the error information in the standard WebAPI format

However null results into the following exception:

System.InvalidOperationException: Writing to the response body is invalid for responses with status code 204.
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ThrowWritingToResponseBodyNotSupported()
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.FirstWriteAsyncInternal(ReadOnlyMemory1 data, CancellationToken cancellationToken) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.FirstWriteAsync(ReadOnlyMemory1 data, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.WritePipeAsync(ReadOnlyMemory1 data, CancellationToken cancellationToken) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.WriteAsync(ReadOnlyMemory1 source, CancellationToken cancellationToken)
at System.Text.Json.JsonSerializer.WriteAsyncCore(Stream utf8Json, Object value, Type inputType, JsonSerializerOptions options, CancellationToken cancellationToken)
at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|21_0(ResourceInvoker invoker, IActionResult result)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|17_1(ResourceInvoker invoker)
at Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)

I have removed all formatters and just using a clean "UseMVC()" in my startup.

[rfcdejong]

Wrong repository, will add to the right one now