Let's ponder over the problem solving process...
1. Read the text file line by line as string values into a List<keyvaluepair><int,>> with randomized integer key
2. Sort this List by its keys.
3. Read this List into an Array.
4. Cycle through this Array to get the randomly sorted texts.
Next, no sweat no gain, get your hands dirty by mixing and matching these examples from the following links to work out your solution:
1.
http://www.dotnetperls.com/streamreader[
^]
2.
http://www.dotnetperls.com/shuffle[
^]
You may begin...