[疑问]树TreeView绑定Xml文件的小例子！

<iewc:treeview id="TreeView1" style="Z-INDEX: 101; LEFT: 176px; POSITION: absolute; TOP: 32px"
                runat="server" TreeNodeSrc="tree3.xml"></iewc:treeview><asp:textbox id="TextBox1" style="Z-INDEX: 102; LEFT: 176px; POSITION: absolute; TOP: 144px"
                runat="server" TextMode="MultiLine" Width="328px" Height="192px"></asp:textbox>

tree3.xml
  <?xml version="1.0" encoding="UTF-8" ?> 
<TREENODES>
<treenode text="Teach Yourself Active Server Pages 3.0 in 21 Days">
  <treenode text="Price $34.95" />
</treenode>   
<treenode text="Authors">
  <treenode text="Mitchell" /> 
  <treenode text="Atkinson" /> 
</treenode>
</TREENODES>

直接写在html页有效

但是我用动态绑定的  TreeNode1.TreeNodeSrc = "Admin.xml";

TreeView1.TreeNodeSrc = "Admin.xml";

TreeView1.Nodes[0].TreeNodeSrc = "Admin.xml";

这3种写法都没有作用，什么原因?