Temperature.cs

public struct Temperature : IEquatable<Temperature>
{
    public Temperature(double celcius)
    {
        this.Celcius = celcius;
    }

    public double Celcius { get; }

    public static bool operator ==(Temperature left, Temperature right)
    {
        return left.Equals(right);
    }

    public static bool operator !=(Temperature left, Temperature right)
    {
        return !left.Equals(right);
    }

    public bool Equals(Temperature other)
    {
        return this.Celcius.Equals(other.Celcius);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj))
        {
            return false;
        }

        return obj is Temperature && this.Equals((Temperature) obj);
    }

    public override int GetHashCode()
    {
        return this.Celcius.GetHashCode();
    }
}

TemperatureChangedEventArgs.cs

public class TemperatureChangedEventArgs : EventArgs
{
    public TemperatureChangedEventArgs(Temperature temperature)
    {
        this.Temperature = temperature;
        this.Time = DateTime.UtcNow;
    }

    public Temperature Temperature { get; }

    public DateTime Time { get; }
}

TemperatureDevice.cs

public class TemperatureDevice
{
    public event EventHandler<TemperatureChangedEventArgs> TemperatureChanged;
}