SqlCommand sqlQuery = new SqlCommand();
            sqlQuery.CommandText = "Select brandOfCar,IdBrand From Brands";            
            DataSet ResultSet = RunQuery(sqlQuery);            

            if (ResultSet.Tables.Count > 0)
            {
                TreeNode parent = new TreeNode("Марки", "Марки");
                TreeNode NewNode, NewNode1;
                foreach (DataRow row in ResultSet.Tables[0].Rows)
                {
                    NewNode = new TreeNode(row["brandOfCar"].ToString());                
                    NewNode.SelectAction = TreeNodeSelectAction.Expand;
                    parent.CollapseAll();
                    parent.ChildNodes.Add(NewNode);

                    string idBrand = row["IdBrand"].ToString();                   
                    sqlQuery.CommandText = "Select nameModel from Models where Models.brandId = " + idBrand;                        
                    sqlQuery.Parameters.Add("nameBrand", SqlDbType.NVarChar).Value = NewNode.Value;
                    ResultModels = RunQuery(sqlQuery);                 

                        foreach (DataRow rowModels in ResultModels.Tables[0].Rows)
                        {
                            NewNode1 = new TreeNode(rowModels["nameModel"].ToString());
                            NewNode1.PopulateOnDemand = true;
                            NewNode1.SelectAction = TreeNodeSelectAction.Expand;
                            NewNode.SelectAction = TreeNodeSelectAction.Select;
                            NewNode.ChildNodes.Add(NewNode1);
                        }                 
                }
                TreeView1.Nodes.Add(parent);