cannot convert from 'method group' to 'TimerCallback'

Question

I'm trying to run function getOrg though hosted services but some how its not working I'm not sure what I'm doing wrong.

Error:

Argument 1: cannot convert from 'method group' to 'TimerCallback' (CS1503)

public class TokenService : IHostedService
{
    public IConfiguration _Configuration { get; }
    protected IMemoryCache _cache;
    private Timer _timer;
    public IHttpClientFactory _clientFactory;

    private readonly IServiceScopeFactory _scopeFactory;

    public TokenService(IConfiguration configuration, IMemoryCache memoryCache, IHttpClientFactory clientFactory, IServiceScopeFactory scopeFactory)
    {
        _Configuration = configuration;
        _cache = memoryCache;
        _clientFactory = clientFactory;
        _scopeFactory = scopeFactory;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _timer = new Timer(getOrg, null, 0, 1000); // getting error here
        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        //Timer does not have a stop. 
        _timer?.Change(Timeout.Infinite, 0);
        return Task.CompletedTask;
    }

    public async Task getOrg()
        {
            var request = new HttpRequestMessage(HttpMethod.Get, "organizations");
            var response = await _client_NP.SendAsync(request);
            var json = await response.Content.ReadAsStringAsync();
            OrganizationsClass.OrgsRootObject model = JsonConvert.DeserializeObject<OrganizationsClass.OrgsRootObject>(json);


            using (var scope = _scopeFactory.CreateScope())
            {
                var _DBcontext = scope.ServiceProvider.GetRequiredService<DBContext>();

                foreach (var item in model.resources)
                {
                    var g = Guid.Parse(item.guid);
                    var x = _DBcontext.Organizations.FirstOrDefault(o => o.OrgGuid == g);
                    if (x == null)
                    {
                        _DBcontext.Organizations.Add(new Organizations
                        {
                            OrgGuid = g,
                            Name = item.name,
                            CreatedAt = item.created_at,
                            UpdatedAt = item.updated_at,
                            Timestamp = DateTime.Now,
                            Foundation = 3
                        });
                    }
                    else if (x.UpdatedAt != item.updated_at)
                    {
                        x.CreatedAt = item.created_at;
                        x.UpdatedAt = item.updated_at;
                        x.Timestamp = DateTime.Now;
                    }
                }

                await getSpace();

                await _DBcontext.SaveChangesAsync();
            }
        }
}

You are using `Timer` [constructor](https://learn.microsoft.com/en-us/dotnet/api/system.threading.timer.-ctor) with [TimerCallback](https://learn.microsoft.com/en-us/dotnet/api/system.threading.timercallback) parameter, which pass a method with following signature: `void SomeName(object state)`. Now look at your `getOrg`. — Sinatr, Aug 21 '19 at 12:58

score 3 · Accepted Answer · answered Aug 21 '19 at 13:00

3

TimerCallback takes on object parameter for state. Try changing getOrg to:

public async void getOrg(object state)

answered Aug 21 '19 at 13:00

Sean

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I need `getOrg` to Task not void my bad something like this public `async Task getOrg(object state)` because there are two other functions that are chained together from `getOrg` and they all are async once those those functions finishes then await `_DBcontext.SaveChangesAsync();` will be executed – Jojo Aug 21 '19 at 13:15
@Jojo - You don't need to make `getOrg` an `async Task` in order to await within `getOrg`. Event handlers is one of the few places where it's acceptable to have an `async void` method. – Sean Aug 21 '19 at 13:17
Sure got it thank you – Jojo Aug 21 '19 at 13:22

score 1 · Answer 2 · answered Aug 21 '19 at 12:59

You are providing wrong parameters to System.Threading.Timer constructor.

The first parameter should be a delegate type (instead of getOrg):

public delegate void TimerCallback(object state);

So add a delegate to your code:

private void TimerProc(object state)
{
}

Change the constructor:

_timer = new Timer(TimerProc, null, 0, 1000); // getting error here

cannot convert from 'method group' to 'TimerCallback'

2 Answers2