Code:

 private void SetTemplateLibraryFolders()
        {
            tvFolders.DataBind();
        }

Code:

Server Error in '/' Application.
--------------------------------------------------------------------------------

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace: 


[ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index]
   System.ThrowHelper.ThrowArgumentOutOfRangeException() +78
   System.Collections.Generic.List`1.get_Item(Int32 index) +53
   System.Web.UI.WebControls.TreeNodeCollection.get_Item(Int32 index) +16
   NOVODUGME.Layouts.NOVODUGME.TemplateSelector.Page_Load(Object sender, EventArgs e) +726
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +42
   System.Web.UI.Control.OnLoad(EventArgs e) +132
   Microsoft.SharePoint.WebControls.UnsecuredLayoutsPageBase.OnLoad(EventArgs e) +101
   Microsoft.SharePoint.WebControls.LayoutsPageBase.OnLoad(EventArgs e) +49
   System.Web.UI.Control.LoadRecursive() +66
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2428

 

Code:
<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %>
<%@ Import Namespace="Microsoft.SharePoint.ApplicationPages" %>
<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %>
<%@ Register TagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"%>
<%@ Import Namespace="Microsoft.SharePoint" %>
<%@ Assembly Name="Microsoft.Web.CommandUI, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="TemplateSelector.aspx.cs" Inherits="NOVODUGME.Layouts.NOVODUGME.TemplateSelector" DynamicMasterPageFile="~masterurl/default.master"  %>


<asp:Content ID="PageHead" ContentPlaceHolderID="PlaceHolderAdditionalPageHead" runat="server">
<script language='javascript' type="text/javascript">
    // Open template with the corresponding Office app
    function OpenNewTemplate(strTemplate, strSaveLocation) {
        var strProgID = "SharePoint.OpenDocuments";
        createNewDocumentWithProgID(makeAbsUrl(strTemplate),makeAbsUrl(strSaveLocation), strProgID, false);
        window.frameElement.commitPopup();
    }
</script>
 

</asp:Content>

<asp:Content ID="Main" ContentPlaceHolderID="PlaceHolderMain" runat="server"  >
<div>
<div id="Navigation" style="position: absolute; top: 0; left: 0; width: 30em">

 <asp:Label ID="Label1" Text="Please select the document(s) from the Tree" runat="server"></asp:Label> <br />  
<asp:placeholder id="placeHolder" runat="server" />
</div>
<div id="Content" style="margin-left: 30em;">
    <asp:ListView ID="lvTemplates" runat="server" GroupItemCount="5" DataKeyNames="Title">
        <LayoutTemplate>
             <table cellpadding="5" runat="server" id="tblTemplates">
                 <tr id="groupplaceholder" runat="server"></tr>
              </table>
         </LayoutTemplate>
         <GroupTemplate>
          <tr id="itemPlaceholderContainer" runat="server" style="height: 80px;">
            <td id="itemPlaceholder" runat="server">
            </td>
          </tr>
        </GroupTemplate>
         <ItemTemplate>
           <td id="Td1" valign="top" align="center" style="width: 100px;" runat="server">
            <asp:HyperLink ID="TemplateLink" runat="server" NavigateUrl='<%# Eval("Url") %>' Target="">
                 
            <asp:Image ID="IconImage" runat="server" ImageUrl='<%# Eval("ImageUrl") %>' />
             <br />
                 
             <%# Eval("Title") %>
            </asp:HyperLink>
           </td>
          </ItemTemplate>
        </asp:ListView>
  </div>
</div>
</asp:Content>

<asp:Content ID="PageTitle" ContentPlaceHolderID="PlaceHolderPageTitle" runat="server">
Application Page
</asp:Content>

<asp:Content ID="PageTitleInTitleArea" ContentPlaceHolderID="PlaceHolderPageTitleInTitleArea" runat="server" >
My Application Page
</asp:Content>

Code:

using System;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.Administration;
using System.Collections;
using System.Data;
using Microsoft.SharePoint.Utilities;
using System.Web;
using System.Web.UI.WebControls;
using System.Web.UI;


namespace NOVODUGME.Layouts.NOVODUGME
{

    public partial class TemplateSelector : LayoutsPageBase
    {
     //disable control form   public override void VerifyRenderingInServerForm(Control control) { }

        // datasource for the Template ListView
        public readonly DataTable _dataTable = new DataTable();

       
        protected override void OnInit(EventArgs e) 
         {  
                base.OnInit(e);  
                createTree();  
          }

        public void createTree()
        {
            SPSecurity.RunWithElevatedPrivileges(delegate() {  
        SPSite currentSite = SPContext.Current.Site;  
        using(SPWeb currentWeb = currentSite.OpenWeb()) {  
            // set the tree view properties  
            SPTreeView treeView = new SPTreeView();
           treeView.EnableClientScript = true;  
            treeView.Target = "_self";
            treeView.ShowLines = true; // show lines   
            treeView.ExpandDepth = 1; // expand non   
            SPList list = currentWeb.Lists["Templates"]; // Document Library   
           TreeNode rootNode = new System.Web.UI.WebControls.TreeNode(list.Title);
           rootNode.SelectAction = TreeNodeSelectAction.SelectExpand;  
            // loop down the tree   
            TraverseFiles(list.RootFolder, rootNode); // Iterate through all Folders   
            // add the root node to tree view   
            treeView.Nodes.Add(rootNode);  
            
            placeHolder.Controls.Add(treeView); // add the Tree view to place Holder which we have added in design   
            _dataTable.Columns.Add("ImageUrl", typeof(string));
            _dataTable.Columns.Add("Title", typeof(string));
            _dataTable.Columns.Add("Url", typeof(string));

            var selectedNode = treeView.SelectedNode == null ? treeView.Nodes[0].Value : treeView.SelectedNode.Value;

            GetTemplatesInSelectedFolder(selectedNode);

            // set the templates as the datasource for the template list view
            lvTemplates.DataSource = _dataTable;
        }  
    });  

        }

       public TreeNode TraverseFiles(SPFolder folder, TreeNode node) {  
    try {  
        // add the files contained in this folder   
       foreach(SPFile file in folder.Files) {  
                // create a new node and add to the tree   
                TreeNode childNode = new System.Web.UI.WebControls.TreeNode(file.Name + " (" + file.TimeLastModified.ToShortDateString() + ")", "", "~/_layouts/images/" + file.IconUrl, file.ServerRelativeUrl.ToString(), "");  
                node.ChildNodes.Add(childNode);  
            }  
            // test if we have child folders   
        bool blnRecurseFolders = folder.SubFolders.Count > 0 ? true : false;  
        // if we have sub folders then loop through them   
        if (blnRecurseFolders) {  
            // loop through the child folders   
            foreach(SPFolder childFolder in folder.SubFolders) {  
                // create a new node and loop through the files   
                TreeNode childNode = new TreeNode();  
                childNode.Text = childFolder.Name;  
                childNode.Value = childFolder.ServerRelativeUrl.ToString();  
                node.ChildNodes.Add(TraverseFiles(childFolder, childNode));  
            }  
        }  
    } catch (Exception e) {  
        //TODO: handle error   
    }  
    return node;  
}
       /// <summary>
       /// Open selected folder of the templates library and fill
       /// the data table with the templates in the folder
       /// </summary>
       /// <param name="folderUrl">Target folder</param>

       private void GetTemplatesInSelectedFolder(string folderUrl)
       {
           using (SPSite site = new SPSite("http://test-net.dri.local"))
           {
               using (SPWeb web = site.OpenWeb())
               {
                   SPList list = web.Lists.TryGetList("Templates");
                   if (list != null)
                   {
                       SPDocumentLibrary docLib = (SPDocumentLibrary)list;
                       SPFolder folder = web.GetFolder(folderUrl);
                       AddFilesToDataTable(web, folder);
                   }
               }
           }
       }
       /// <summary>
       /// Add templates to the data source
       /// </summary>
       /// <param name="docWeb"></param>
       /// <param name="folder"></param>

       private void AddFilesToDataTable(SPWeb docWeb, SPFolder folder)
       {
           foreach (SPFile file in folder.Files)
           {
               // get template icon
               string docIcon = SPUtility.ConcatUrls("/_layouts/images/", SPUtility.MapToIcon(file.Web, SPUtility.ConcatUrls(file.Web.Url, file.Url), "", IconSize.Size32));

               // absolute url of the template
               string absUrl = (string)file.Item[SPBuiltInFieldId.EncodedAbsUrl];
               // click action
               string action;
               if (!String.IsNullOrEmpty(HttpContext.Current.Request.QueryString["Templates"]))
               {
                   // get the list from the List query string
                   Guid? docLibId = new Guid(HttpContext.Current.Request.QueryString["Templates"]);
                   SPList selectedLibrary = docWeb.Lists.GetList(docLibId.Value, true);
                   string docLibUrl = selectedLibrary.DefaultViewUrl;
                   // remove Forms[%] from the view url to get the
                   // correct document library url
                   docLibUrl = docLibUrl.Remove(docLibUrl.LastIndexOf("Forms", StringComparison.Ordinal));
                   action = string.Format("javascript:OpenNewTemplate('{0}', '{1}');", absUrl, SPContext.Current.Site.RootWeb.Url + docLibUrl);
                   AddDataToDataTable(docIcon, file.Name, action);
               }


           }
       }
       /// <summary>
       /// Add template to the data source
       /// </summary>
       /// <param name="docIcon">Template icon</param>
       /// <param name="title">Template title</param>
       /// <param name="url">Template url</param>


       private void AddDataToDataTable(string docIcon, string title, string url)
       {
           DataRow row = _dataTable.NewRow();
           row["ImageUrl"] = docIcon;
           row["Title"] = title;
           row["Url"] = url;
           _dataTable.Rows.Add(row);
       }
      


 


    }
}

Code:

  const string serverURL = "http://test-net/";
                public string ServerURL
                {
                    get
                    {
                        return serverURL;
                    }
                }

                protected void Page_Load(object sender, EventArgs e)
            {
                if (!IsPostBack)
                {

                    SetTemplateLibraryFolders();
                }
              
                      _dataTable.Columns.Add("ImageUrl", typeof(string));
                     _dataTable.Columns.Add("Title", typeof(string));
                    _dataTable.Columns.Add("Url", typeof(string));
                   var selectedNode = tvFolders.SelectedNode == null ? tvFolders.Nodes[0].Value : tvFolders.SelectedNode.Value;

                   GetTemplatesInSelectedFolder(selectedNode);
                // set the templates as the datasource for the template list view
                  lvTemplates.DataSource = _dataTable;

             }

         protected void SetTemplateLibraryFolders()
                {
                    
                 
                        using (ClientContext clientcontext = new ClientContext(ServerURL))
                        {
                            
                            //Load Libraries from SharePoint
                     //     clientcontext.Load(clientcontext.Web.Lists);
                     //     clientcontext.ExecuteQuery();
                      //   foreach (List list in clientcontext.Web.Lists)
                       //   {
                         //      ddlLists.Items.Add(list.Title);
                            // btnLoad_Click(btnLoad, new EventArgs());
                      //     }

                            List listTemplates = clientcontext.Web.Lists.GetByTitle("Templates");
                            clientcontext.Load(listTemplates);
                            clientcontext.ExecuteQuery();
                            clientcontext.Load(listTemplates.RootFolder);
                            clientcontext.Load(listTemplates.RootFolder.Folders);
                            clientcontext.ExecuteQuery();
                            tvFolders.ShowLines = true;
                            TreeNode RootNode = new TreeNode(listTemplates.Title);
                            tvFolders.Nodes.Add(RootNode);

                            IterateListItems(RootNode, listTemplates.RootFolder, clientcontext);

                            foreach (Folder SubFolder in listTemplates.RootFolder.Folders)
                            {
                                if (SubFolder.Name != "Forms")
                                {
                                    TreeNode TopNode = new TreeNode(SubFolder.Name);
                                    RootNode.ChildNodes.Add(TopNode);
                                    IterateListItems(TopNode, SubFolder, clientcontext);
                                    IterateFolders(TopNode, SubFolder, clientcontext);
                                }
                            }
                        }
                        tvFolders.ExpandAll();
                        tvFolders.ShowLines = true;
                                        
                   
                  
                }