private ObservableCollection <Folder> GetFiles()
        {
            var      nodeImageInfo = new ObservableCollection <Folder>();
            Assembly assembly      = typeof(NodeWithImage).GetTypeInfo().Assembly;

            var doc = new Folder()
            {
                FileName = "Documents", ImageIcon = "Doc.png"
            };
            var download = new Folder()
            {
                FileName = "Downloads", ImageIcon = "Doc.png"
            };
            var mp3 = new Folder()
            {
                FileName = "Music", ImageIcon = "Doc.png"
            };
            var pictures = new Folder()
            {
                FileName = "Pictures", ImageIcon = "Doc.png"
            };
            var video = new Folder()
            {
                FileName = "Videos", ImageIcon = "Doc.png"
            };

            var pollution = new File()
            {
                FileName = "Environmental Pollution.docx", ImageIcon = "Word.png"
            };
            var globalWarming = new File()
            {
                FileName = "Global Warming.ppt", ImageIcon = "PP.png"
            };
            var sanitation = new File()
            {
                FileName = "Sanitation.docx", ImageIcon = "Word.png"
            };
            var socialNetwork = new File()
            {
                FileName = "Social Network.pdf", ImageIcon = "PDF_Icon.png"
            };
            var youthEmpower = new File()
            {
                FileName = "Youth Empowerment.pdf", ImageIcon = "PDF_Icon.png"
            };

            var games = new File()
            {
                FileName = "Game.exe", ImageIcon = "EXE.png"
            };
            var tutorials = new File()
            {
                FileName = "Tutorials.zip", ImageIcon = "Zip.png"
            };
            var typeScript = new File()
            {
                FileName = "TypeScript.7z", ImageIcon = "Zip.png"
            };
            var uiGuide = new File()
            {
                FileName = "UI-Guide.pdf", ImageIcon = "PDF_Icon.png"
            };

            var song = new File()
            {
                FileName = "Gouttes", ImageIcon = "Audio.png"
            };

            var camera = new File()
            {
                FileName = "Camera Roll", ImageIcon = "Doc.png"
            };
            var stone = new File()
            {
                FileName = "Stone.jpg", ImageIcon = "Png.png"
            };
            var wind = new File()
            {
                FileName = "Wind.jpg", ImageIcon = "Png.png"
            };

            var img0 = new SubFile()
            {
                FileName = "WIN_20160726_094117.JPG", ImageIcon = "People_Circle6.png"
            };
            var img1 = new SubFile()
            {
                FileName = "WIN_20160726_094118.JPG", ImageIcon = "People_Circle5.png"
            };

            var video1 = new File()
            {
                FileName = "Naturals.mp4", ImageIcon = "Video.png"
            };
            var video2 = new File()
            {
                FileName = "Wild.mpeg", ImageIcon = "Video.png"
            };

            doc.Files = new ObservableCollection <File>
            {
                pollution,
                globalWarming,
                sanitation,
                socialNetwork,
                youthEmpower
            };

            download.Files = new ObservableCollection <File>
            {
                games,
                tutorials,
                typeScript,
                uiGuide
            };

            mp3.Files = new ObservableCollection <File>
            {
                song
            };

            pictures.Files = new ObservableCollection <File>
            {
                camera,
                stone,
                wind
            };
            camera.SubFiles = new ObservableCollection <SubFile>
            {
                img0,
                img1
            };

            video.Files = new ObservableCollection <File>
            {
                video1,
                video2
            };

            nodeImageInfo.Add(doc);
            nodeImageInfo.Add(download);
            nodeImageInfo.Add(mp3);
            nodeImageInfo.Add(pictures);
            nodeImageInfo.Add(video);

            checkedItems = new ObservableCollection <object>();
            checkedItems.Add(pollution);
            checkedItems.Add(sanitation);
            checkedItems.Add(youthEmpower);
            checkedItems.Add(camera);
            checkedItems.Add(video1);
            checkedItems.Add(video1);
            checkedItems.Add(typeScript);
            checkedItems.Add(typeScript);

            return(nodeImageInfo);
        }