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

树形控件是使用频率很高的一种控件。对于属性控件往往需要下面两个功能

1.TreeList带有CheckBox，并且节点要有三种状态（所有的子节点都选中，所有的子节点都没选择，一部分子节点选中）。使用 DevXpress的TreeList控件很容易实现这一功能。

设置TreeList.OptionsView.ShowCheckBoxes = true            //是否显示CheckBox

设置TreeList.OptionsBehavior.AllowIndeterminateCheckState = true;         //设置节点是否有中间状态，即一部分子节点选中，一部分子节点没有选中

设置这两个属性之后就实现了TreeList带有CheckBox,并且节点有三种状态。

2.选中父节点或者子节点相互影响的功能，如选择父节点选择所有子节点。绑定TreeList的两个事件AfterCheckNode和 BeforeCheckNode

实现功能的代码如下：

        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);
        }

        /// <summary>
        /// 设置子节点的状态
        /// </summary>
        /// <param name="node"></param>
        /// <param name="check"></param>
        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);
            }
        }

        /// <summary>
        /// 设置父节点的状态
        /// </summary>
        /// <param name="node"></param>
        /// <param name="check"></param>
        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);
            }
        }