Error handling (Sending ex.Message to the client)

Here is an simple error DTO class

public class ErrorDto
{
    public int Code {get;set;}
    public string Message { get; set; }

    // other fields

    public override string ToString()
    {
        return JsonConvert.SerializeObject(this);
    }
}

And then using the ExceptionHandler middleware:

            app.UseExceptionHandler(errorApp =>
            {
                errorApp.Run(async context =>
                {
                    context.Response.StatusCode = 500; // or another Status accordingly to Exception Type
                    context.Response.ContentType = "application/json";

                    var error = context.Features.Get<IExceptionHandlerFeature>();
                    if (error != null)
                    {
                        var ex = error.Error;

                        await context.Response.WriteAsync(new ErrorDto()
                        {
                            Code = <your custom code based on Exception Type>,
                            Message = ex.Message // or your custom message
                            // other custom data
                        }.ToString(), Encoding.UTF8);
                    }
                });
            });