Use whitesapce instead of \r\n...
<samplefirst>(\s)*<samplesecond>
Sample code for C#...
Regex oRegex = new Regex( @"<samplefirst>(\s)*<samplesecond>" );
MatchCollection oMatchCollection = oRegex .Matches( string.Format( "<samplefirst>{0} {0}<samplesecond><samplefirst>{0}no{0}<samplesecond>", Environment.NewLine ) );