Devexpress treelist 树形控件 CheckBox 实现带三种状态

 Devexpress treelist 树形控件 CheckBox 实现带三种状态（全部选中，部分选中，全部没选中）

1、两个属性：

       this.treeList1.OptionsView.ShowCheckBoxes = true;  //是否显示CheckBox
       this.treeList1.OptionsBehavior.AllowIndeterminateCheckState = true; //设置节点是否有中间状态

2、绑定TreeList的两个事件AfterCheckNode和 BeforeCheckNode：

      private void treeList1_AfterCheckNode(object sender, DevExpress.XtraTreeList.NodeEventArgs e)
        {
            SetCheckedChildNodes(e.Node, e.Node.CheckState);
            SetCheckedParentNodes(e.Node, e.Node.CheckState);
        }

        private void treeList1_BeforeCheckNode(object sender, DevExpress.XtraTreeList.CheckNodeEventArgs e)
        {
            e.State = (e.PrevState == CheckState.Checked ? CheckState.Unchecked : CheckState.Checked);
        }

3、两个方法：

       /// 设置子节点的状态
 
        private void SetCheckedChildNodes(DevExpress.XtraTreeList.Nodes.TreeListNode node, CheckState check)
        {
            for (int i = 0; i < node.Nodes.Count; i++)
            {
                node.Nodes[i].CheckState = check;
                SetCheckedChildNodes(node.Nodes[i], check);
            }
        }


        /// 设置父节点的状态
 
        private void SetCheckedParentNodes(DevExpress.XtraTreeList.Nodes.TreeListNode node, CheckState check)
        {
            if (node.ParentNode != null)
            {
                bool b = false;
                CheckState state;
                for (int i = 0; i < node.ParentNode.Nodes.Count; i++)
                {
                    state = (CheckState)node.ParentNode.Nodes[i].CheckState;
                    if (!check.Equals(state))
                    {
                        b = !b;
                        break;
                    }
                }
                node.ParentNode.CheckState = b ? CheckState.Indeterminate : check;
                SetCheckedParentNodes(node.ParentNode, check);
            }
        }