How to bind TextBox to a nullable property only if a CheckBox is checked

Question

I need to bind TextBox.Text to a property if the CheckBox next to it is checked. Otherwise the value of property should be null.

Let's say DTO Class is like:

public class DataForInputDTO 
{
    public double? Power {get; set;}
    public double? Speed {get; set;} 
    // Other Properties
}

Now, when user unchecks the Speed CheckBox the TextBox next to it gets disabled (This is OK) but I also need the property Speed to get null instead of 60. Is there any way to do this without manually changing the binding at CheckBox.CheckedChaneg?

Answer 1

You can set via the property to which the Speed CheckBox is bound to. For example, if the IsChecked Property of Speed checkbox is bound to a property called IsSpeedChecked, you could do the following.

    private double _powerValue = 0;

    public double? Power { get; set; } = 0;

    public bool IsPowerEnabled
    {
        get => _isPowerEnabled;
        set
        {
            _isPowerEnabled = value;
            if (!value)
            {
                _powerValue = Power.Value;
                Power = null;
            }
            else
            {
                Power = _powerValue;
            }
            NotifyOfPropertyChange(nameof(Power));
            NotifyOfPropertyChange(nameof(IsPowerEnabled));
        }
    }