simplify the sayurin's code @ https://github.com/sayurin/HereDocumentExtension/blob/master/HereDocumentExtension/HereDocumentExtention.cs

HereDoc.cs

/// <summary>
/// [Rules]
/// - all of lines (except first&last) require same indent
/// 		* indent = mix of tab and space is ok
/// - first line requires empty (only line break)
/// 		* linebreak = CR+LF or LF
/// - last line requires "no line break"
/// 
/// [SpecialThanks]
/// this code is same as sayurin's code (http://git.io/iE1MhA)
/// 
/// [Usage]
/// var x = @"
/// 			test
/// 				test".AsHereDocSimple();
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static string AsHereDocSimple(this string input)
{        			
	return Regex.Replace(input,
	                    @"^(?=(?<sep>\r?\n)(?<indent>[ \t]*))(\k<sep>\k<indent>(?<text>[^\r\n]*))*$",
	                     m => string.Join(
	                    	m.Groups["sep"].Value,
	                    	m.Groups["text"].Captures.Cast<Capture>().Select(c => c.Value)));
}