Merge pull request microsoft#1150 from brianrob/regex

Undo Revert of Regex Compilation

src/PerfView/EtwEventSource.cs

@@ -646,6 +646,8 @@ internal ETWEventRecord(ETWEventSource source, TraceEvent data, Dictionary<strin
 
             #region private
 
+            private static readonly Regex specialCharRemover = new Regex(" *[\r\n\t]+ *", RegexOptions.Compiled);
+
             /// <summary>
             /// Adds 'fieldName' with value 'fieldValue' to the output.  It either goes into a column (based on columnOrder) or it goes into
             /// 'rest' as a fieldName="fieldValue" string.   It also updates 'columnSums' for the fieldValue for any in a true column 
@@ -658,7 +660,7 @@ private void AddField(string fieldName, string fieldValue, Dictionary<string, in
                 }
                 // If the field value has to many newlines in it, the GUI gets confused because the text block is larger than
                 // the vertical size.   WPF may fix this at some point, but in the mean time this is a work around. 
-                fieldValue = Regex.Replace(fieldValue, " *[\r\n\t]+ *", " ");
+                fieldValue = specialCharRemover.Replace(fieldValue, " ");
 
                 var putInRest = true;
                 if (columnOrder != null)

src/TraceEvent/DynamicTraceEventParser.cs

@@ -1018,6 +1018,8 @@ protected internal override Delegate Target
             }
         }
 
+        private static readonly Regex paramReplacer = new Regex(@"%(\d+)", RegexOptions.Compiled);
+
         public override string GetFormattedMessage(IFormatProvider formatProvider)
         {
             if (MessageFormat == null)
@@ -1027,7 +1029,7 @@ public override string GetFormattedMessage(IFormatProvider formatProvider)
 
             // TODO is this error handling OK?  
             // Replace all %N with the string value for that parameter.  
-            return Regex.Replace(MessageFormat, @"%(\d+)", delegate (Match m)
+            return paramReplacer.Replace(MessageFormat, delegate (Match m)
             {
                 int targetIndex = int.Parse(m.Groups[1].Value) - 1;