LayoutFarm.Text.EditableTextFlowLayer.InsertLine C# (CSharp) Method

        void InsertLine(int insertAt, EditableTextLine textLine)
        {
            if (insertAt < 0)
            {
                throw new NotSupportedException();
            }

            List<EditableTextLine> lines = lineCollection as List<EditableTextLine>;
            if (lines != null)
            {
                int j = lines.Count;
                if (insertAt > j - 1)
                {
                    AppendLine(textLine);
                }
                else
                {
                    EditableTextLine line = lines[insertAt];
                    int cy = line.Top;
                    textLine.SetTop(cy);
                    textLine.SetLineNumber(insertAt);
                    cy += line.ActualLineHeight;
                    for (int i = insertAt; i < j; i++)
                    {
                        line = lines[i];
                        line.SetTop(cy);
                        line.SetLineNumber(i + 1);
                        cy += line.ActualLineHeight;
                    }
                    textLine.editableFlowLayer = this;
                    lines.Insert(insertAt, textLine);
                }
            }
            else
            {
                lines = new List<EditableTextLine>();
                lines.Add((EditableTextLine)lineCollection);
                lineCollection = lines;
                FlowLayerHasMultiLines = true;
                int j = lines.Count;
                if (insertAt > j - 1)
                {
                    AppendLine(textLine);
                }
                else
                {
                    EditableTextLine line = lines[insertAt];
                    int cy = line.Top;
                    textLine.SetTop(cy);
                    textLine.SetLineNumber(insertAt);
                    cy += line.ActualLineHeight;
                    for (int i = insertAt; i < j; i++)
                    {
                        line = lines[i];
                        line.SetTop(cy);
                        line.SetLineNumber(i + 1);
                        cy += line.ActualLineHeight;
                    }
                    textLine.editableFlowLayer = this;
                    lines.Insert(insertAt, textLine);
                }
            }
        }