Returns a copy of this string object converted to lowercase using the casing rules of the invariant culture.
The invariant culture represents a culture that is culture-insensitive. It is associated with the English language but not with a specific country or region. For more information, see Using the InvariantCulture Property.
If your application depends on the case of a string changing in a predictable way that is unaffected by the current culture, use the string.ToLowerInvariant method. The string.ToLowerInvariant method is equivalent to ToLower(CultureInfo.InvariantCulture). The method is recommended when a collection of strings must appear in a predictable order in a user interface control.
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 lowercase.