How to control what part of a UIView to update (iOS/Xamarin) - I need to prevent the screen from being fully erased -

I takes in a stream of'm working on a drawing application data and displays it turns out that UIView (too slow drawing a lot of line segments in the core graphics) I only by drawing a portion of the screen, I'm trying to speed it up with the new data

I currently screen ( Using this function of Xamarin / Monotouch)

  NSTimer.CreateRepeatingScheduledTimer (TimeSpan.FromSeconds (0.1), representatives {pane.SetNeedsDisplay ();});   
 where pane is my UIView object pane object needs to know that reprinted the edge of the screen itself. I think there is another way that specifies the area of ​​the screen to be underlined - is this the right way? Or some other solution?  
 In addition, a group of code grids draws these never change there is a way to save them to some layer or something so that I can just add in the background?  
 Though the options to go along with Opening is not as good as drawing lines and I have to apply a lot of additional code to make it look perfect.  
 Thank you!   
  
 graph data, you own Uaiviyuu subclass'  drawRect:  method Core graphics should be used to present the lines. Ensure that the method only overlaps the data that overlaps with the CRGRTAR logic. Method > Need a redraw method, so instead of using the entire UIView mark as when changing your graph data, you should use the  setNeedsDisplayInRect method of UIView: point to There is a new thing for  that area of ​​UIView is the data that will call  drawRect: , which will be re-created only if (if you implemented it correctly) )  
 About the background grid. , You can render a UIImage the grid, so to demonstrate that UIImage draws the graph behind the scenes. ,  UIGraphicsGetImageFromCurrentImageContext , and  UIGraphicsEndImageContext : You  UIGraphicsBeginImageContext , I want to see the documentation for the  CALayer renderInContext.