/// <summary>
/// Retain the specified character from this set if it is present.
/// Upon return this set will be empty if it did not contain <paramref name="c"/>, or
/// will only contain c if it did contain <paramref name="c"/>.
/// </summary>
/// <param name="set">This set.</param>
/// <param name="c">The character to be retained.</param>
/// <returns>This object, for chaining.</returns>
/// <draft>ICU4N 60.1</draft>
/// <provisional>This API might change or be removed in a future release.</provisional>
public static UnicodeSet Retain(this UnicodeSet set, int c)
{
if (set == null)
{
throw new ArgumentNullException(nameof(set));
}
return(set.Retain(c));
}