Working on the assumption that a paragraph is separated by by a carriage return/line feed (char 13, 10) then it's quite simple.
string filePath = @"c:\temp\doc.txt";
System.IO.FileStream fs = System.IO.File.OpenRead(filePath);
byte[] binaryData = new byte[fs.Length];
fs.Read(binaryData, 0, binaryData.Length);
string text = System.Text.Encoding.ASCII.GetString(binaryData);
string[] paragraphs = text.Split('\r').Select(m => m.Trim('\n')).ToArray();