How i can pick a random word from a textbox and then remove it from there?

am new to C# and am trying to do the following:

I Have a textbox that contains for example "Astronomy (from Greek: ἀστρονομία) is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets...etc."

when i click a button, i want the program to select a random word from the above textbox (Ignoring 2 char words like "in" or "to"), then remove it from there and save it in another variable for later use.