private void GetSelectedTreeNode(TreeNodeCollection nodes, List<TreeNode> selectedNodes)
        {
foreach (TreeNode node in nodes)
            {
if (node.Checked)
                {
                    selectedNodes.Add(node);
                }
                GetSelectedTreeNode(node.Nodes, selectedNodes);
            }
        }

List<TreeNode> selectedNodes=new List<TreeNode>();
            GetSelectedTreeNode(treeView1.Nodes, selectedNodes);
foreach (TreeNode node in selectedNodes)
            {
                a += node.Name + ",";
            }
            MessageBox.Show(a.Trim(','));