My name
is
Jon Skeet

Is there a way for a property to set its backing value?

I have a property, and I want it to set another property whenever it's being set. For example:

    private double Bpm
    {
        set
        {
            <myself> = value;
            _bps = <myself> / 60;
        }
        get
        {
            return <myself>;
        }
    }

What I actually did is the following, because I couldn't find another way:

    private double _bpm;
    private double _bps;

    private double Bpm
    {
        set
        {
            _bpm = value;
            _bps = _bpm / 60;
        }
        get
        {
            return _bpm;
        }
    }

I find it not elegant, having two private members Bpm and _bpm. I can also have a SetBpm method, but I want to know if this is achievable with properties.

A property is just a pair of methods, really - and if you use an automatically-implemented property, the compiler implements them for you and creates a field. You want one field - because you've only got one real value, and two views on it - so you can either get the compiler to create that field for you automatically by using an automatically-implemented property, or you can declare it yourself. I'd use an automatically-implemented property, personally. Then you calculate the other property based on the original. You can either make that a read-only property, or make it read-write.

For example, as a read-only version:

public double BeatsPerSecond { get; set; }
public double BeatsPerMinute { get { return BeatsPerSecond * 60; } }

Or in C# 6:

public double BeatsPerSecond { get; set; }
public double BeatsPerMinute => BeatsPerSecond * 60;

For a read-write version:

public double BeatsPerSecond { get; set; }
public double BeatsPerMinute
{
    get { return BeatsPerSecond * 60; }
    set { BeatsPerSecond = value / 60; }
}

You could decide to make BeatsPerMinute the "stored" one instead, should you wish, and just change the property calculation.

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