/// <summary>
/// Within a specified input string, replaces all groups with the specified number that match the regular expression with a string where each character is replaced with the specified character.
/// </summary>
/// <param name="regex">The regular expression to be matched.</param>
/// <param name="input">The string to search for a match.</param>
/// <param name="replacementChar">The replacement char.</param>
/// <param name="groupNumber">A number of the group.</param>
/// <exception cref="ArgumentNullException"><paramref name="regex"/> or <paramref name="input"/> is <c>null</c>.</exception>
public static string ReplaceGroupChar(this Regex regex, string input, char replacementChar, int groupNumber)
{
if (regex == null)
{
throw new ArgumentNullException(nameof(regex));
}
if (input == null)
{
throw new ArgumentNullException(nameof(input));
}
return(RegexReplace.ReplaceGroups(regex, input, groupNumber, group => new string(replacementChar, group.Length)));
}
