Returns a copy of this string converted to uppercase, using the casing rules of the specified culture.
The casing rules of the culture specified by the culture parameter determine the way the case of a string is changed.
This method does not modify the value of the current instance. Instead, it returns a new string in which all characters in the current instance are converted to uppercase.
If you pass the string.ToUpper(System.Globalization.CultureInfo) method a System.Globalization.CultureInfo object other than System.Globalization.CultureInfo.InvariantCulture, the casing operation will take culture-specific rules into account. If you need the lowercase or uppercase version of an operating system identifier, such as a file name, named pipe, or registry key, use the string.ToLowerInvariant or string.ToUpperInvariant method. This produces the same result in every culture and performs more efficiently.