Help! Calling a method

 I need help on calling a method. This code is not working:
 
 
protected void treeMain_SelectedNodeChanged(object sender, EventArgs e)
{
if (treeMain.SelectedNode.ChildNodes.Count == 0)
{
BookList List = new BookList();

Info = List.getBookInfo(this.treeMain.SelectedNode.Value);

txtId.Text = Info.TITLE_ID;


} } Basically their are two objects: BookInfo, and BookList. Here is what the directions say: "If a book node is selected, you need to create an Instance of BookList(which I have above) and call its ...