TreeView states that it is unable to find CSS style, XML file or images. The ASPX page is in subfolder.

You should use the tilde ("~") symbol. It is an abbreviation for the home directory of web application. Tilde can be used in property values, XML Structure, CSS Style, templates, etc.

This feature is very useful because User Control with a TreeView can be placed on the ASPX pages, which are located in different subdirectories of the web application.

Examples of using:

[ASPX]

  StructureFileURL="~/Structures/TreeView.xml"
  SkinFolder="~/Skins/GrayScale/"

[XML]

  <item title="Subfolder Page" href = "~/Subfolder/Default.aspx" />

[CSS]

  .ItemDIVe
  {
    cursor:default;
    padding:3px;
    background-image:url(~/Skins/Stone/ItemOver.jpg);
    ...
  }

The CSS style can include the tilde ("~") symbol only if the TreeView component loads the CSS style from a Skin Folder as specified by the CSSSource property.