binding a usercontrol to the opposite of a bool property

Question

Pretty straightforward: I\'m looking to do the same as this but in winforms. Everything that google seems to pull up is wpf specific (ie. I don\'t want to reference presentation

Answer 1

Based on Adam's answer I wrote a small helper class:

class NegateBinding
{
    string propertyName;
    object dataSource;
    string dataMember;
    public NegateBinding(string propertyName, object dataSource, string dataMember)
    {
        this.propertyName = propertyName;
        this.dataSource = dataSource;
        this.dataMember = dataMember;
    }

    public static implicit operator Binding(NegateBinding eb)
    {
        var binding = new Binding(eb.propertyName, eb.dataSource, eb.dataMember, false, DataSourceUpdateMode.OnPropertyChanged);
        binding.Parse += new ConvertEventHandler(negate);
        binding.Format += new ConvertEventHandler(negate);
        return binding;
    }

    static void negate(object sender, ConvertEventArgs e)
    {
        e.Value = !((bool)e.Value);
    }
}

Now you can use it like this:

label1.DataBindings.Add(new NegateBinding("Visible", otherObject, "HasData"));

Answer 2

To do this, I´d do a readonly property named NotSomeBool, in the same class where you have the property SomeBool, and bind to this property instead.

Answer 3

You have two options:

1. Create the Binding object manually and attach to the Format and Parse events and swap the value in each.
2. Create an additional property on the class that just reverses the logic of the intended property

The first option is cleaner, IMO, as it doesn't force your class's API to follow your UI design, though the second option is (marginally) easier.

Example of Option 1

private void SwitchBool(object sender, ConvertEventArgs e)
{ 
    e.Value = !((bool)e.Value);
}

...

Binding bind = new Binding("Checked", this.object, "SomeBool");

bind.Format += SwitchBool;
bind.Parse += SwitchBool;

CheckBox1.DataBindings.Add(bind);

Example of Option 2

public class SomeClass
{
    public bool SomeBool { get; set; }

    public bool NotSomeBool
    {
        get { return !SomeBool; }
        set { SomeBool = !value; }
    }
}

...

CheckBox1.DataBindings.Add("Checked", this.object, "NotSomeBool");

Again, I very much favor option 1, since option 2 requires that you tailor your class to your UI design.