# Writing Custom Checks


To create a custom check, create a new custom check class:

<!-- snippet: CustomCheck -->

```cs
public class MyCustomCheck :
    CustomCheck
{
    public MyCustomCheck()
        : base("SomeId-StartUp", "SomeCategory")
    {

    }

    public override Task<CheckResult> PerformCheck(CancellationToken cancellationToken = default)
    {
        if (SomeService.GetStatus())
        {
            return CheckResult.Pass;
        }

        return CheckResult.Failed("Some service is not available.");
    }
}
```

<!-- endsnippet -->

When the custom check executes, it should return a pass or fail status and, in the case of failure, a descriptive message. This status and descriptive message will be sent to ServiceControl and will appear in the [ServicePulse UI](in-servicepulse.md) and in [ServiceControl integration events](notification-events.md).

All custom checks are executed when the endpoint starts up. If the optional interval is specified, the custom check will be executed periodically.

<!-- snippet: PeriodicCheck -->

```cs
public class MyPeriodicCheck :
    CustomCheck
{
    public MyPeriodicCheck()
        : base("SomeId-Periodic", "SomeCategory", TimeSpan.FromSeconds(5))
    {
    }

    public override Task<CheckResult> PerformCheck(CancellationToken cancellationToken = default)
    {
        if (SomeService.GetStatus())
        {
            return CheckResult.Pass;
        }

        return CheckResult.Failed("Some service is not available.");
    }
}
```

<!-- endsnippet -->

> [!NOTE]
> Custom checks are discovered at runtime using assembly scanning. This means they can also be deployed to endpoints as NuGet packages.