Changing case in string:
We can change the case of letters with in a string with two methods one is ToUpper() and another is ToLower() :
Public string ToLowere(); // lowercases all letters
Public string ToUpper(); // uppercases all letters
There is also version of these methods that allows us to specify cultural setting one is ToUpperInvariant and another is ToLowerInvariant. These work as same as ToUpper and ToLower except culture to perform the transformation to upper or lower cases