Converts the value of a Unicode character to its lowercase equivalent using the casing rules of the invariant culture.
The lowercase equivalent of the c parameter, or the unchanged value of c, if c is already lowercase or not alphabetic.
If your application is unaffected by the current culture and depends on the case of a character changing in a predictable way, then use the char.ToLowerInvariant(char) method. The char.ToLowerInvariant(char) method is equivalent to ToLower(Char, CultureInfo.InvariantCulture).
Use string.ToLowerInvariant to convert a string to lowercase.