IgnorePatternWhitespace-Option:
Specifies that un-escaped white space is excluded from the pattern and enables comments following a number sign '#'. Note that white space is never eliminated from within a character class. For a list of escaped white-space characters, see the Escapes section.
http://okapi.sourceforge.net/Release/Shared/Help/regex.htm#Options

//alle Zeilen mit 2 aufeinanderfolgenden Leerzeichen
Regex demo1 = @"\ \ ".AsRegex();

Regex spaceOnNewLineRegex = @"\n\ +".AsRegex();
Regex spaceafterLineRegex = @"\ +\n".AsRegex();

//alle Zeilen mit 2 aufeinanderfolgenden Leerzeichen
Regex demo1 = @"\s\s".AsRegex();

Regex spaceOnNewLineRegex = @"\n\s+".AsRegex();
Regex spaceafterLineRegex = @"\s+\n".AsRegex();