Select only one node in Treeview

private void treeView1_AfterCheck(object sender, TreeViewEventArgs e)
       {
           if (e.Node.Checked)
           {
               //selectParentNodes(e.Node.Parent);
               selectChildNodes(e.Node.Nodes);
           }
           else
           {
               //DiselectParentNodes(e.Node.Parent);
               DiselectChildNodes(e.Node.Nodes);
           }
       }

private void selectChildNodes(TreeNodeCollection childes)
       {
           foreach (TreeNode oneChild in childes)
           {
               if (oneChild.Checked==false)
                   oneChild.Checked = true;
               selectChildNodes(oneChild.Nodes);
           }
       }

private void DiselectChildNodes(TreeNodeCollection childes)
       {
           foreach (TreeNode oneChild in childes)
           {
               if (oneChild.Checked)
                   oneChild.Checked = false;
               DiselectChildNodes(oneChild.Nodes);
           }
       }