Add readonly modifier for regex

src/Logic/SubtitleFormats/AdobeEncore.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AdobeEncore : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d ", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d ", RegexOptions.Compiled);
         private int _maxMsDiv10 = 0;
 
         public override string Extension

src/Logic/SubtitleFormats/AdobeEncoreLineTabNewLine.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AdobeEncoreLineTabNewLine : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d\d\d\d \d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d\t", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d\d\d\d \d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d\t", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/AdobeEncoreLineTabs.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AdobeEncoreLineTabs : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d\d\d\d\t\d\d:\d\d:\d\d:\d\d\t\d\d:\d\d:\d\d:\d\d\t", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d\d\d\d\t\d\d:\d\d:\d\d:\d\d\t\d\d:\d\d:\d\d:\d\d\t", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/AdobeEncoreTabs.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AdobeEncoreTabs : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d\t\d\d:\d\d:\d\d:\d\d\t", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d\t\d\d:\d\d:\d\d:\d\d\t", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/AdobeEncoreWithLineNumbers.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AdobeEncoreWithLineNumbers : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d+ \d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d ", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d+ \d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d ", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/AdobeEncoreWithLineNumbersNtsc.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AdobeEncoreWithLineNumbersNtsc : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d+ \d\d;\d\d;\d\d;\d\d \d\d;\d\d;\d\d;\d\d ", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d+ \d\d;\d\d;\d\d;\d\d \d\d;\d\d;\d\d;\d\d ", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/AvidCaption.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class AvidCaption : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d$", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d \d\d:\d\d:\d\d:\d\d$", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/CapMakerPlus.cs

@@ -10,7 +10,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
     public class CapMakerPlus : SubtitleFormat
     {
 
-        private static Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d$", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d\d:\d\d:\d\d:\d\d$", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/YouTubeTranscript.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class YouTubeTranscript : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d{1,3}:\d\d$", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d{1,3}:\d\d$", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/SubtitleFormats/YouTubeTranscriptOneLine.cs

@@ -8,7 +8,7 @@ namespace Nikse.SubtitleEdit.Logic.SubtitleFormats
 {
     public class YouTubeTranscriptOneLine : SubtitleFormat
     {
-        private static Regex regexTimeCodes = new Regex(@"^\d{1,3}:\d\d.+$", RegexOptions.Compiled);
+        private static readonly Regex regexTimeCodes = new Regex(@"^\d{1,3}:\d\d.+$", RegexOptions.Compiled);
 
         public override string Extension
         {

src/Logic/TimeCode.cs

@@ -5,7 +5,7 @@ namespace Nikse.SubtitleEdit.Logic
 {
     public class TimeCode
     {
-        public static TimeCode MaxTime = new TimeCode(99, 59, 59, 999);
+        public static readonly TimeCode MaxTime = new TimeCode(99, 59, 59, 999);
 
         public const double BaseUnit = 1000.0; // Base unit of time
         private double _totalMilliseconds;