C#

if (e.Button == MouseButtons.Right)
{
   Point point = new Point(e.X, e.Y);
   TreeNode node = treeView.GetNodeAt(point);
   if (node == null)
	return;
   
   treeView.SelectedNode = node;
   if (node.Tag is TypeX)
   {
	XContextMenu.Show(treeView, point);
   }
   else if (node.Tag is TypeY)
   {
      YContextMenu.Show(treeView, point);
   }
}		

public abstract class Filter
{
    public abstract bool Evalutate();
}

public class BooleanFilter : Filter
{
    private bool value;
    public BooleanFilter(bool value)
    {
        this.value = value;
    }
 
    public override bool Evaluate()
    {
        return value;
    }
}

public class AndFilter : Filter
{
    private Filter filterA;
    private Filter filterB;

    public AndFilter(Filter filterA, Filter filterB)
    {
        this.filterA = filterA;
        this.filterB = filterB;
    }
 
    public override bool Evaluate()
    {
        // Remember in the OrFilter version to change the & to an |
        bool result = filterA.Evaluate() & filterB.Evaluate();
        return result;
    }
}

BooleanFilter a = new BooleanFilter(false);
BooleanFilter b = new BooleanFilter(false);
BooleanFilter c = new BooleanFilter(true);
BooleanFilter d = new BooleanFilter(true);
 
AndFilter andAB = new AndFilter(a, b); // andAB.Evaluate() == false;
AndFilter andBC = new AndFilter(b, c); // andBC.Evaluate() == false;
OrFilter orBC = new OrFilter(b, c); // orBC.Evaluate() == true;
 
// a OR b OR c - Combines the result of previous OrFilter with a BooleanFilter
Filter aOrBOrC = OrFilter(a, orBC);
 
// Watch the way the query is being built up though:
// a AND b OR c == (a AND (b OR c)) 
Filter aAndBOrC = AndFilter(a, orBC);