There are many string routines in C#. Many of them are called using dot notation and are called methods. A complete list of string manipulation methods can be found at Internet. ;
Let's get acquainted with a couple of the simplest and most useful of them.
string s = "aAbBcC11"
string sUp = s.ToUpper() // sUp = "AABBCC11" - a method that converts each character of a string to uppercase
string sLow = s.ToLower() // sLow = "aabbcc11" - a method that converts each character of a string to lowercase
To the left of the dot is the name of the string (or the string itself in quotes) to which the method is to be applied, and to the right of the dot is the name of the method. The method is always written with parentheses. Any parameters can go inside the brackets if they are needed.