ICSharpCode.AvalonEdit.TextEditor.AppendText C# (CSharp) Method

        public void AppendText(string textData)
        {
            var document = GetDocument();
            document.Insert(document.TextLength, textData);
        }

        //...........................................................

        public void ConstructViewers <EDITOR_T> ()
            where EDITOR_T : avalon.TextEditor, new()
        {
            m_viewerL = new EDITOR_T();  PanelL.Children.Add(m_viewerL);
            m_viewerR = new EDITOR_T();  PanelR.Children.Add(m_viewerR);

            // disable folding:
            // can't listen for folding events, can't sync foldings between viewers
            // todo: more generic solution if add folding to types other than xml.
            var viewerL = m_viewerL as XmlViewer;
            var viewerR = m_viewerR as XmlViewer;

            if (viewerL != null && viewerR != null)
            {
                avalon.Folding.FoldingManager.Uninstall(viewerL.FoldingManager);
                avalon.Folding.FoldingManager.Uninstall(viewerR.FoldingManager);
            }

            m_viewerL.HorizontalScrollBarVisibility = ScrollBarVisibility.Auto;
            m_viewerL.VerticalScrollBarVisibility   = ScrollBarVisibility.Hidden;

            m_viewerR.HorizontalScrollBarVisibility = ScrollBarVisibility.Auto;
            m_viewerR.VerticalScrollBarVisibility   = ScrollBarVisibility.Hidden;

            foreach (var line in m_model.OldText.Lines)
            {
                var text = line?.Text + System.Environment.NewLine;
                m_viewerL.AppendText(text);
            }
            foreach (var line in m_model.NewText.Lines)
            {
                var text = line?.Text + System.Environment.NewLine;
                m_viewerR.AppendText(text);
            }

            m_renderL = new TextDifferBackgroundRenderer(m_viewerL);
            m_renderR = new TextDifferBackgroundRenderer(m_viewerR);

            m_renderL.Lines = m_model.OldText.Lines;
            m_renderR.Lines = m_model.NewText.Lines;

            m_viewerL.TextArea.TextView.BackgroundRenderers.Add(m_renderL);
            m_viewerR.TextArea.TextView.BackgroundRenderers.Add(m_renderR);

            m_viewerL.TextArea.TextView.VisualLinesChanged  += ViewerL_VScrollChanged;
            m_viewerL.TextArea.TextView.ScrollOffsetChanged += ViewerL_HScrollChanged;
            m_viewerL.LayoutUpdated += ViewerL_LayoutUpdated;

            m_viewerR.TextArea.TextView.VisualLinesChanged  += ViewerR_VScrollChanged;
            m_viewerR.TextArea.TextView.ScrollOffsetChanged += ViewerR_HScrollChanged;

            Loaded += OnLoaded;
        }