In my previous post I have asked for excel-like functionlity for column grouping and hiding (not possible). Below there is a solution which almost works, problems are described at the bottom. NA2010 vol 3 was used.

Step 1: Create and assign creation filter

MyGridFilter filter = new MyGridFilter();

private void Form1_Load(object sender, EventArgs e)
{
            m_gridVariant.CreationFilter = filter;
}

Step 2 : filter implementation

 public class MyGridFilter : IUIElementCreationFilter
    {
        public void AfterCreateChildElements(UIElement parent)
        {
            HeaderUIElement header = parent as HeaderUIElement;
            if (header != null && header.Header.Column == null) //this will ensure its a group header
            {
                //region remove old instances (if present)
                foreach (UIElement e in header.ChildElements)
                {
                    if (e is MyCheckboxUIElement)
                        header.ChildElements.Remove(e);
                }
               
                //create new element
                MyCheckboxUIElement ele = new MyCheckboxUIElement(header);
               
                //gather group columns so that you know what to hide
                foreach (UltraGridColumn col in header.Header.Group.Columns)
                    ele.AddColumn(col);

                //add to child elements
                header.ChildElements.Add(ele);
            }
        }

        public bool BeforeCreateChildElements(UIElement parent){ return false; }
    }

Step 3 : Implement my checkbox so that it could do the hiding job

 public class MyCheckboxUIElement : CheckBoxUIElement
    {
        public MyCheckboxUIElement(UIElement parent) : base(parent)
        {
            //set checkbox rectangle
            int x, y, w, h;
            w = 20;
            h = parent.RectInsideBorders.Height - 2;
            x = parent.RectInsideBorders.Right - 22;
            y = parent.RectInsideBorders.Y + 2;
            this.Rect = new Rectangle(x, y, w, h);

            //base.ButtonStyle = UIElementButtonStyle.WindowsVistaButton; //how?
            base.CheckState = System.Windows.Forms.CheckState.Unchecked;
            base.ThreeState = false;
            base.ButtonType = UIElementButtonType.Toggle; //have no effect on appearance
        }
        protected override void OnCheckStateChange()
        {
            base.OnCheckStateChange();

            if (base.CheckState == System.Windows.Forms.CheckState.Checked)
                foreach (UltraGridColumn col in myColumns)
                    col.Hidden = true;
            else
                foreach (UltraGridColumn col in myColumns)
                    col.Hidden = false;
        }

}

Problems/Questions:

#1 When using base.IsChecked instead of base.CheckState it always returns false value. Checkbox acts properly - one mouse click makes it "checked", why IsChecked doe not work?

#2 Implementation above works, but following things are happening:

a.) when user clicks checkbox for the first time columns become hidden, but checkbox is turned back to unchecked state after it was handled. OnCheckStateChange is not triggered

b.) When columns are still hidden, checkbox is still unchecked, user clicks on it it changes from unchecked to checked (code has no effect, columns are already hidden)

c.) unchecking the checkbox causes column to appear just fine.

What and why is happenning in 2a, that causes checkbox to uncheck on it's own after columns are hidden. Are there any events I could handle?