There are many different ways to lowercase and uppercase strings in the C# language, transforming "ABC" to "abc" and back again. However, some ways are more efficient and lead to faster code than others, and sometimes you don't need to change cases at all.
Case-Insensitive string.Equals Method
Char Lowercase Optimization
char.IsLower Methods
char.ToLower Methods
String IsUpper and IsLower Methods
ToLower String Method
ToLowerInvariant and ToUpperInvariant Methods
ToUpper Method
Uppercase First Letter
Uppercase Words in String