Reading Data

You can query health data from Apple HealthKit and Android Health Connect using the IHealthService interface. Always request read permissions first.

Querying Health Data

public class HealthDashboardViewModel(IHealthService health)
{
    async Task LoadDataAsync()
    {
        // 1. Request permissions (read-only shorthand)
        var result = await health.RequestPermissions(
            DataType.StepCount,
            DataType.HeartRate,
            DataType.Calories,
            DataType.Distance
        );

        // Or request per-metric read/write permissions in a single call
        // await health.RequestPermissions(
        //     (PermissionType.Read, DataType.StepCount),
        //     (PermissionType.Read, DataType.HeartRate),
        //     (PermissionType.Write, DataType.Weight),
        //     (PermissionType.ReadWrite, DataType.BloodPressure)
        // );

        // 2. Check which permissions were granted
        foreach (var (type, success) in result)
        {
            if (!success)
                Console.WriteLine($"Permission denied for {type}");
        }

        // 3. Query data for the last 24 hours
        var end = DateTimeOffset.Now;
        var start = end.AddDays(-1);

        var steps = (await health.GetStepCounts(start, end, Interval.Days)).Sum(x => x.Value);
        var calories = (await health.GetCalories(start, end, Interval.Days)).Sum(x => x.Value);
        var distance = (await health.GetDistances(start, end, Interval.Days)).Sum(x => x.Value);
        var heartRate = (await health.GetAverageHeartRate(start, end, Interval.Days)).Average(x => x.Value);

        // 4. Blood pressure returns a special result type
        var bp = await health.GetBloodPressure(start, end, Interval.Days);
        if (bp.Any())
        {
            var avgSystolic = bp.Average(x => x.Systolic);
            var avgDiastolic = bp.Average(x => x.Diastolic);
        }

        // 5. Hourly breakdown
        var hourlySteps = await health.GetStepCounts(start, end, Interval.Hours);
        foreach (var bucket in hourlySteps)
        {
            Console.WriteLine($"{bucket.Start:g} - {bucket.End:g}: {bucket.Value:N0} steps");
        }
    }
}

Real-Time Observation

See the dedicated Observing Data page for streaming health data changes via IAsyncEnumerable<HealthResult>.

Best Practices

1. Always request permissions first — Call RequestPermissions before reading data
2. Use appropriate intervals — Interval.Days for summaries, Interval.Hours for detailed breakdowns
3. Handle empty results — Check .Any() before calling .Average() to avoid InvalidOperationException
4. Use CancellationToken — Pass cancellation tokens for long-running queries
5. Sum vs Average — Use .Sum() for cumulative metrics (steps, calories, distance, hydration, sleep) and .Average() for point-in-time metrics (heart rate, weight, height, body fat, O2 sat, resting HR)
6. Blood pressure is special — It returns BloodPressureResult (not NumericHealthResult) with separate Systolic and Diastolic values