PropertyChanged不触发

Question

I have a strange situation:

in a .NET CF project there is a class (call it A) which has the following structure:

public partial class A: Form, INotifyPropertyChanged
{
//for simplicity stripping off everything unrelated to this problem

        private int _SelectedRowsCount = 0;
        public int SelectedRowsCount
        {
            get { return _SelectedRowsCount; }
            set
            {
                _SelectedRowsCount = value;
                OnPropertyChanged("SelectedRowsCount");
            }
        }

        public bool enableCollectionButton
        {
            get { return SelectedRowsCount > 0; }
        }

//....
//
//


         void SomeMethod()
{
 //for simplicity:
SelectedRowsCount = 1; //<- HERE NOT FIRING Propertychanged for enableCollectionButton
}
}

The class implements correctly the INotifyPropertyChanged interface which makes the the SelectedRowsCount property to fire a property changed notification (i evaluated this with the debugger). The enableCollectionButton property is databound to some control like so:

someButton.DataBindings.Add("Enabled", this, "enableCollectionButton");

But the enableCollectionButton property does not change (though depending on the value of SelectedRowsCount). This property should be evaluated on a change of the SelectedRowsCount property, BUT IS NOT!!!

Why is this not functioning, what do i miss??

Thanks in advance

Answer 1

Try this

public partial class A: Form, INotifyPropertyChanged
{
//for simplicity stripping off everything unrelated to this problem

    private int _SelectedRowsCount = 0;
    public int SelectedRowsCount
    {
        get { return _SelectedRowsCount; }
        set
        {
            _SelectedRowsCount = value;
            OnPropertyChanged("SelectedRowsCount");
            OnPropertyChanged("enableCollectionButton"); //This changes too !
        }
    }

    public bool enableCollectionButton
    {
        get { return SelectedRowsCount > 0; }
    }
}

What happens is that you're binding to the enableCollectionButton property, but you're not notifying the BindingManager of the change to enableCollectionButton , rather of the change to SelectedRowsCount . The BindingManager doesn't know they're related!

Also try using Microsoft's naming conventions , enableCollectionButton should be EnableCollectionButton