C#: Remove duplicates in keywords + regexp optimisation + don't use c…

…aptures if not needed

components/prism-csharp.js

@@ -2,15 +2,15 @@ Prism.languages.csharp = Prism.languages.extend('clike', {
 	'keyword': /\b(abstract|as|async|await|base|bool|break|byte|case|catch|char|checked|class|const|continue|decimal|default|delegate|do|double|else|enum|event|explicit|extern|false|finally|fixed|float|for|foreach|goto|if|implicit|in|int|interface|internal|is|lock|long|namespace|new|null|object|operator|out|override|params|private|protected|public|readonly|ref|return|sbyte|sealed|short|sizeof|stackalloc|static|string|struct|switch|this|throw|true|try|typeof|uint|ulong|unchecked|unsafe|ushort|using|virtual|void|volatile|while|add|alias|ascending|async|await|descending|dynamic|from|get|global|group|into|join|let|orderby|partial|remove|select|set|value|var|where|yield)\b/,
 	'string': [
 		{
-			pattern: /@("|')(\1\1|\\\1|\\?(?!\1)[\s\S])*\1/,
+			pattern: /@("|')(?:\1\1|\\[\s\S]|(?!\1)[^\\])*\1/,
 			greedy: true
 		},
 		{
-			pattern: /("|')(\\?.)*?\1/,
+			pattern: /("|')(?:\\.|(?!\1)[^\\\r\n])*?\1/,
 			greedy: true
 		}
 	],
-	'number': /\b-?(0x[\da-f]+|\d*\.?\d+f?)\b/i
+	'number': /\b-?(?:0x[\da-f]+|\d*\.?\d+f?)\b/i
 });
 
 Prism.languages.insertBefore('csharp', 'keyword', {
@@ -29,7 +29,7 @@ Prism.languages.insertBefore('csharp', 'keyword', {
 		inside: {
 			// highlight preprocessor directives as keywords
 			'directive': {
-				pattern: /(\s*#)\b(define|elif|else|endif|endregion|error|if|line|pragma|region|undef|warning)\b/,
+				pattern: /(\s*#)\b(?:define|elif|else|endif|endregion|error|if|line|pragma|region|undef|warning)\b/,
 				lookbehind: true,
 				alias: 'keyword'
 			}