ASP.NET Core middleware which return Exception as text on response body (useful when using swagger UI to test API in development instead of default HTML view)

ASP.NET Core middleware return Exception as text on response body

using System;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Diagnostics;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

internal class ExceptionInResponseMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<ExceptionInResponseMiddleware> _logger;

    public ExceptionInResponseMiddleware(
        RequestDelegate next,
        ILogger<ExceptionInResponseMiddleware> logger)
    {
        _next = next;
        _logger = logger;
    }

    public async Task Invoke(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            if (!context.Response.HasStarted)
            {
                _logger.LogDebug("Caught exception: '{message}'. Sending as part of the response.", ex.Message);

                context.Response.StatusCode = StatusCodes.Status500InternalServerError;
                context.Response.ContentType = "text/plain";

                var responseBody = ex.ToString();
                context.Response.ContentLength = Encoding.UTF8.GetByteCount(responseBody);
                await context.Response.WriteAsync(responseBody);

                if (!(context.Features.Get<IExceptionHandlerFeature>() is ExceptionHandlerFeature exceptionFeature))
                {
                    exceptionFeature = new ExceptionHandlerFeature();
                    context.Features.Set<IExceptionHandlerFeature>(exceptionFeature);
                }

                exceptionFeature.Error = ex;
            }
            else
            {
                _logger.LogWarning("Response has started. Cannot modify it.");
            }
        }
    }
}