in IOptionsSnapshot<T>, T must have a public parameterless contstructor

[cilerler]

I would like to be able to log errors in my option/setting file. If I use DI in it, caller says in IOptionsSnapshot<GracePeriodManagerServiceSetting>, GracePeriodManagerServiceSetting must have a public parameterless contstructor how can I make this work?

GracePeriodManagerService.cs

public GracePeriodManagerService(IOptionsSnapshot<GracePeriodManagerServiceSetting> options)
...

GracePeriodManagerServiceSetting.cs

    public class GracePeriodManagerServiceSetting
    {
        private readonly ILogger _logger;
        public GracePeriodManagerServiceSetting(ILogger<GracePeriodManagerServiceSetting> logger)
        {
            _logger = logger;
        }
    ...
    }

appsettings.json

{
  "GracePeriodManagerService": {
    "DelayTime": "1 2 3 4 5 6"
  }
}

[fubar-coder]

I'm in the same boat as you. I guess that the short answer about how to get this work is: You don't. The reasoning probably was, that configuring the options should be a lightweight operation, so that it usually doesn't need services which may use some heavy-weight initialization.

[cilerler]

I hear you but I believe it should be developers decision and not "opinionated" view.

[davidfowl]

Logging from a poco, is kinda code smell no? Why are you logging from your settings object that isn't supposed to have behavior? What does GracePeriodManagerServiceSetting look like?

[cilerler]

I don't think so.

Simple scenario would be a background service I would like to run in specific time based on crontab string. And I use ncrontab where value in appsettings.json will be string but I need to extract next date in options.

Now consider that I want to use that setting in multiple places. It becomes really ugly to implement it.

appsettings.json

{
  "GracePeriodManagerService": {
    "DelayTime": "1 2 3 4 5"
  }
}

GracePeriodManagerServiceSetting.cs (the one I have right now)

using System;
using NCrontab;

namespace MyProject.Api.Services.GracePeriodManagerService
{
    public class Setting
    {
        public const string ConfigurationSectionName = nameof(GracePeriodManagerService);

        private string _delayTime;
        public string DelayTime
        {
            get
            {
                if (_delayTime == null)
                {
                    return null;
                }

                try
                {
                    CrontabSchedule crontab = CrontabSchedule.Parse(_delayTime, new CrontabSchedule.ParseOptions { IncludingSeconds = true });
                    DateTime nextOccurrence = crontab.GetNextOccurrence(DateTime.UtcNow);
                    return nextOccurrence.ToString("s");
                }
                catch (CrontabException ce)
                {
                    //_logger.LogError(ce, ce.Message);
                    throw;
                }
                catch (Exception e)
                {
                    //_logger.LogError(e, e.Message);
                    throw;
                }
            }
            set => _delayTime = value;
        }
    }
}

[HaoK]

To consume services to configure your options, you don't do it in the ctor, you can consume services inside of your IConfigure[Named]Options<T>

[HaoK]

A generic implementation of this that we do to make this easier is found here to give you a concrete example of what that would look like: https://github.com/aspnet/Options/blob/maestro/master/src/Microsoft.Extensions.Options/ConfigureNamedOptions.cs#L66

[cilerler]

@HaoK would you please elaborate on that and provide a working example please?

[poke]

@cilerler Could you show exactly what you would like to log and how from your GracePeriodManagerServiceSetting class? I agree with David here that logging from the options POCO is a sign for code smell. You can probably do this better by moving the logging logic elsewhere.

From the example you have given using the configuration manager, it is unclear though what you are actually trying to do (and how that contradicts David’s comment).

[HaoK]

Rough idea of the code you need to consume services would be the following, I do agree with the other comments that this seems like a lot of work just to log stuff here

// services.AddTransient<IConfigureOptions<GracePeriodManagerServiceSetting>, MyConfigure>();
public class MyConfigure : IConfigureOptions<GracePeriodManagerServiceSetting> {
    public MyConfigure(ILogger<GracePeriodManagerServiceSetting> logger) => _logger = logger;
   public Configure(GracePeriodManagerServiceSetting s) { // use _logger }
}

[poke]

@HaoK I’m not sure if this is really about configuring the options (since there is still a mention of an appsettings.json) but rather consuming the options and then parsing it into a higher level object. And that parsing process could fail and these failures should be logged. At least that’s how I am currently interpreting this.

[cilerler]

@poke please locate GracePeriodManagerServiceSetting.cs above and look for commented //_logger.LogError(ce, ce.Message); lines. Well you just posted another message and it is exactly what I'm trying to do.

@HaoK would you mind revisiting my question, it is about evaluating the setting value and reporting it and I don't think Configure may useful here. (or I still don't get it what you are trying to point out) 👼