c# - Automatic scrolling of textbox choppy -

i redirecting cmd output multi-line textbox, i'm trying auto-scroll down using following code:

textbox1.selectionstart = textbox1.text.length; textbox1.scrolltocaret(); textbox1.refresh(); 

however it's choppy looking, mean, each time line comes in, positions scroll bar @ top of textbox, bottom, it's hard describe made .gif of happening: http://i.imgur.com/mudqrzy.gif

is there way fix it?

for same purpose use richtextbox:

richtextbox1.appendtext(cmdoutputmsg + "\r\n"); richtextbox1.scrolltocaret(); 

in way new text added @ end of existing text, , scrolltocaret focus remains on last inserted text.

i think normal textbox work in same way.