Fix for Regex performance issue when compiled Regex is used with RegexOptions.IgnoreCase or RegexOptions.CultureInvariant.

Alois-xx · Alois-xx · commit e151e932f86e · 2018-10-18T22:53:06.000+02:00
This saves over 40% in these cases.
diff --git a/src/System.Text.RegularExpressions/tests/RegexCompilationInfoTests.cs b/src/System.Text.RegularExpressions/tests/RegexCompilationInfoTests.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
+using System.Diagnostics;
 using Xunit;
 
 namespace System.Text.RegularExpressions.Tests
@@ -65,6 +66,20 @@ public void MatchTimeout_GetSet_Throws(TimeSpan matchTimeout)
                 regexCompilationInfo.MatchTimeout = matchTimeout);            
         }
 
+        [Fact]
+        public void Compile_To_Assembly()
+        {
+            var rex = new Regex(".*(/Common.Controls.Wpf;component/Themes/)[^/]*.xaml", RegexOptions.Compiled | RegexOptions.IgnoreCase);
+            const string noMatch = "This is a long string which contains no matches at all. Sorry for that";
+            var sw = Stopwatch.StartNew();
+            for(int i=0;i<100*1000;i++)
+            {
+                Assert.False(rex.IsMatch(noMatch));
+            }
+            sw.Stop();
+            Console.WriteLine($"Did take: {sw.Elapsed.TotalSeconds}s");
+        }
+
         [Theory]
         [MemberData(nameof(MatchTimeout_GetSet_Success_MemberData))]
         public void MatchTimeout_GetSet_Success(TimeSpan matchTimeout)
