.NET Core Error Message

error.md

From middleware:

return httpContext.Response.WriteAsync(new ErrorDTO
{
    Message = "Some Message",
    Title = "Some Title
}).ToString();

From Controller:

return BadRequest(new ErrorDTO
{
    Message = "Some Message",
    Title = "Some Title"
});

DTO:

public class ErrorDTO
{
    public string Message { get; set; }
    public string Title { get; set; }

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

Get back JSON:

{"Message":"Some Message", "Title":"Some Title"}