private void TreeSqlServer_AfterSelect(object sender, TreeViewEventArgs e)
        {
            List <string> tList = new List <string>();

            foreach (var item in list)
            {
                if (item.ServerName == e.Node.Text)
                {
                    TreeSqlServer.Nodes[TreeSqlServer.SelectedNode.Index].Nodes.Clear();
                    tList = SqlOperations.GetDbName(item.ServerName, item.Username, item.PassWord);

                    for (int i = 0; i < tList.Count; i++)
                    {
                        TreeSqlServer.Nodes[TreeSqlServer.SelectedNode.Index].Nodes.Add(tList[i]);
                    }

                    TreeSqlServer.ExpandAll();
                }
            }
        }