Tree view in Wpf(xaml)

public void PopulateTreeView(  string dirValue, TreeNode parentNode )
      {
         /*   dirValue = inputTextBox.Text
              parentNode = directoryTreeView.Nodes[0] ..
          * 
             directoryTreeView is a Treeview 
          */


          // array stores all subdirectories in the directory
         string[] directoryArray =  Directory.GetDirectories( dirValue);
 
         try
         {
            // subdirectories are present
            if ( directoryArray.Length != 0 )
            {
               //  create new TreeNode,
               
               foreach ( string directory in directoryArray )
               {
                   // substringDirectory is a string defined in generall
           substringDirectory = Path.GetFileNameWithoutExtension(directory );
                 
                 
                   // current directory
                  TreeNode myNode = new TreeNode( substringDirectory );
                   
                  // add current directory node to parent node
                  parentNode.Nodes.Add( myNode );

                  // recursive populate
                  PopulateTreeView( directory, myNode );
               } 
            } 
         } 

        
         catch ( UnauthorizedAccessException )
         {
            parentNode.Nodes.Add( "Access denied !" );
         }
      }

please explain clearly or post a snippet code (cause I'm new in xaml). Tanx

I've posted this question here but it doesn't help me.