OnRender method in wpf

public class EditorControl : Control
{
    void EditorTextBoxControl_TextChanged(object sender, TextChangedEventArgs e)
            {
                if(_bIsNewScriptLoaded)
                RaiseEditorTextChangedEvent();
        //need to call here
     }
}
 public class LineMargin : FrameworkElement
{
 protected override void OnRender(System.Windows.Media.DrawingContext drawingContext)
 {
	Rect rect = EditorText.GetRectFromCharacterIndex(charIndex);
         	   //this is the height of each line in textEditor.
         	   if (rect.IsEmpty == true)
          	      lineHeight = 0;
          	  else
          	      lineHeight = rect.Height;

         	   for (int i = 0; lineNumber <= _Controller.GetLineCount(); i++, lineNumber++)
           	 {
            	  	  //var foreground = (Brush)GetValue(Control.ForegroundProperty);
                
              	 	 FormattedText text = new FormattedText(
                                                        lineNumber.ToString(CultureInfo.CurrentCulture),
                                                        CultureInfo.GetCultureInfo("en-us"),
                                                        FlowDirection.LeftToRight,
                                                        new Typeface("Verdana"),
                                                        emSize,
                                                        Brushes.SteelBlue);

           	    	 drawingContext.DrawText(text, new Point(renderSize.Width - text.Width,
                                                        (lineHeight * i)  + 2));//2 is a buffer as the number should be displayed little below the rectangle height.
         	   }	
}
}