diff --git a/AdventOfCode/AOC.Tests/Y2015/Day01.cs b/AdventOfCode/AOC.Tests/Y2015/Day01.cs
index a89d303..1cbfd0d 100644
--- a/AdventOfCode/AOC.Tests/Y2015/Day01.cs
+++ b/AdventOfCode/AOC.Tests/Y2015/Day01.cs
@@ -24,7 +24,7 @@ namespace AOC.Tests.Y2015
         [TestCase(")))", -3)] // Example data
         [TestCase(")())())", -3)] // Example data
         [TestCase(null, 232)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             var lines = input != null ? input : realData;
 
@@ -45,7 +45,7 @@ namespace AOC.Tests.Y2015
         [TestCase(")", 1)] // Example data
         [TestCase("()())", 5)]
         [TestCase(null, 1783)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             var lines = input != null ? input : realData;
 
@@ -79,4 +79,4 @@ namespace AOC.Tests.Y2015
             Console.WriteLine($"Part 2: {result}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2015/Day02.cs b/AdventOfCode/AOC.Tests/Y2015/Day02.cs
index 1c88ae4..228af27 100644
--- a/AdventOfCode/AOC.Tests/Y2015/Day02.cs
+++ b/AdventOfCode/AOC.Tests/Y2015/Day02.cs
@@ -18,7 +18,7 @@ namespace AOC.Tests.Y2015
         [TestCase("2x3x4", 58)]
         [TestCase("1x1x10", 43)]
         [TestCase(null, 1606483)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? new[] { input } : realData;
 
@@ -53,7 +53,7 @@ namespace AOC.Tests.Y2015
         [TestCase("2x3x4", 34)]
         [TestCase("1x1x10", 14)]
         [TestCase(null, 3842356)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? new[] { input } : realData;
 
@@ -86,4 +86,4 @@ namespace AOC.Tests.Y2015
             Console.WriteLine($"Part 2: {totalRibbon}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2015/Day03.cs b/AdventOfCode/AOC.Tests/Y2015/Day03.cs
index 7f7b458..7983345 100644
--- a/AdventOfCode/AOC.Tests/Y2015/Day03.cs
+++ b/AdventOfCode/AOC.Tests/Y2015/Day03.cs
@@ -47,7 +47,7 @@ namespace AOC.Tests.Y2015
         [TestCase("^>v<", 4)]
         [TestCase("^v^v^v^v^v", 2)]
         [TestCase(null, 2565)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string lines = input != null ? input : realData;
             int currentX = 0;
@@ -102,7 +102,7 @@ namespace AOC.Tests.Y2015
         [TestCase("^>v<", 3)]
         [TestCase("^v^v^v^v^v", 11)]
         [TestCase(null, 2639)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string lines = input != null ? input : realData;
             int currentX = 0;
@@ -194,4 +194,4 @@ namespace AOC.Tests.Y2015
             Console.WriteLine($"Part 2: {numberOfHousesVisited}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2015/Day04.cs b/AdventOfCode/AOC.Tests/Y2015/Day04.cs
index 6e749d5..de53a5c 100644
--- a/AdventOfCode/AOC.Tests/Y2015/Day04.cs
+++ b/AdventOfCode/AOC.Tests/Y2015/Day04.cs
@@ -46,7 +46,7 @@ namespace AOC.Tests.Y2015
         [TestCase("abcdef", 609043)]
         [TestCase("pqrstuv", 1048970)]
         [TestCase(null, 254575)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string lines = input != null ? input : realData;
 
@@ -61,7 +61,7 @@ namespace AOC.Tests.Y2015
         }
 
         [TestCase(null, 1038736)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string lines = input != null ? input : realData;
 
@@ -75,4 +75,4 @@ namespace AOC.Tests.Y2015
             Console.WriteLine($"Part 2: {i}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2015/Day05.cs b/AdventOfCode/AOC.Tests/Y2015/Day05.cs
index cf0749a..d3c8608 100644
--- a/AdventOfCode/AOC.Tests/Y2015/Day05.cs
+++ b/AdventOfCode/AOC.Tests/Y2015/Day05.cs
@@ -139,7 +139,7 @@ namespace AOC.Tests.Y2015
         [TestCase("haegwjzuvuyypxyu", 0)]
         [TestCase("dvszwmarrgswjxmb", 0)]
         [TestCase(null, 258)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? new[] { input } : realData;
 
@@ -166,7 +166,7 @@ namespace AOC.Tests.Y2015
         [TestCase("uurcxstgmygtbstg", 0)]
         [TestCase("ieodomkazucvgmuy", 0)]
         [TestCase(null, 53)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? new[] { input } : realData;
 
@@ -188,4 +188,4 @@ namespace AOC.Tests.Y2015
             Console.WriteLine($"Part 2: {niceCount}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2015/Day06.cs b/AdventOfCode/AOC.Tests/Y2015/Day06.cs
index 29cf2ce..5ab48a8 100644
--- a/AdventOfCode/AOC.Tests/Y2015/Day06.cs
+++ b/AdventOfCode/AOC.Tests/Y2015/Day06.cs
@@ -93,7 +93,7 @@ namespace AOC.Tests.Y2015
         [TestCase("toggle 0,0 through 999,0", 1000)]
         [TestCase("turn on 0,0 through 999,999/nturn off 499,499 through 500,500", 999996)]
         [TestCase(null, 400410)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("/n") : realData;
 
@@ -121,7 +121,7 @@ namespace AOC.Tests.Y2015
         [TestCase("turn on 0,0 through 0,0", 1)]
         [TestCase("toggle 0,0 through 999,999", 2000000)]
         [TestCase(null, 15343601)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("/n") : realData;
 
@@ -142,4 +142,4 @@ namespace AOC.Tests.Y2015
             Console.WriteLine($"Part 2: {totalBrightness}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2021/Day01.cs b/AdventOfCode/AOC.Tests/Y2021/Day01.cs
index 543cb3d..37c2414 100644
--- a/AdventOfCode/AOC.Tests/Y2021/Day01.cs
+++ b/AdventOfCode/AOC.Tests/Y2021/Day01.cs
@@ -16,7 +16,7 @@ namespace AOC.Tests.Y2021
 
         [TestCase("199,200,208,210,200,207,240,269,260,263", 7)] // Example data
         [TestCase(null, 1681)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             var lines = input != null ? input.Split(',') : realData;
 
@@ -46,7 +46,7 @@ namespace AOC.Tests.Y2021
 
         [TestCase("199,200,208,210,200,207,240,269,260,263", 5)] // Example data
         [TestCase(null, 1704)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             var lines = input != null ? input.Split(',') : realData;
 
@@ -84,4 +84,4 @@ namespace AOC.Tests.Y2021
             Console.WriteLine($"Part 2: {numberOfBiggerSlidingTotals}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2022/Day01.cs b/AdventOfCode/AOC.Tests/Y2022/Day01.cs
index f9cfc62..df3ebd3 100644
--- a/AdventOfCode/AOC.Tests/Y2022/Day01.cs
+++ b/AdventOfCode/AOC.Tests/Y2022/Day01.cs
@@ -29,7 +29,7 @@ namespace AOC.Tests.Y2022
 
 10000", 24000)]
         [TestCase(null, 70764)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -75,7 +75,7 @@ namespace AOC.Tests.Y2022
 
 10000", 45000)]
         [TestCase(null, 203905)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -107,4 +107,4 @@ namespace AOC.Tests.Y2022
             Console.WriteLine($"Part 2: {result}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2022/Day02.cs b/AdventOfCode/AOC.Tests/Y2022/Day02.cs
index d17f4d4..0d2e2fb 100644
--- a/AdventOfCode/AOC.Tests/Y2022/Day02.cs
+++ b/AdventOfCode/AOC.Tests/Y2022/Day02.cs
@@ -18,7 +18,7 @@ namespace AOC.Tests.Y2022
 B X
 C Z", 15)]
         [TestCase(null, 8392)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -36,7 +36,7 @@ C Z", 15)]
 B X
 C Z", 12)]
         [TestCase(null, 1783)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -174,4 +174,4 @@ C Z", 12)]
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2022/Day03.cs b/AdventOfCode/AOC.Tests/Y2022/Day03.cs
index b08d6cd..0151ad7 100644
--- a/AdventOfCode/AOC.Tests/Y2022/Day03.cs
+++ b/AdventOfCode/AOC.Tests/Y2022/Day03.cs
@@ -76,7 +76,7 @@ wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
 ttgJtRGJQctTZtZT
 CrZsJsPPZsGzwwsLwLmpwMDw", 157)]
         [TestCase(null, 8176)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
             List<char> items = new();
@@ -112,7 +112,7 @@ wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
 ttgJtRGJQctTZtZT
 CrZsJsPPZsGzwwsLwLmpwMDw", 70)]
         [TestCase(null, 2689)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
             List<char> items = new();
@@ -141,4 +141,4 @@ CrZsJsPPZsGzwwsLwLmpwMDw", 70)]
             Console.WriteLine($"Part 2: {result}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day01.cs b/AdventOfCode/AOC.Tests/Y2023/Day01.cs
index 99d374e..cdd0e15 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day01.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day01.cs
@@ -21,7 +21,7 @@ pqr3stu8vwx
 a1b2c3d4e5f
 treb7uchet", 142)]
         [TestCase(null, 53080)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -60,7 +60,7 @@ zoneight234
         [TestCase("three2six8two5", 35)]
         [TestCase("eightjzqzhrllg1oneightfck", 88)]
         [TestCase(null, 53268)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -153,4 +153,4 @@ zoneight234
             return finalNumber;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day02.cs b/AdventOfCode/AOC.Tests/Y2023/Day02.cs
index 7d2ae92..8f97fc7 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day02.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day02.cs
@@ -37,7 +37,7 @@ Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
 Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
 Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green", 8)]
         [TestCase(null, 1734)] // The actual answer
-        public void Part1(string input, int? expected)
+        public void Part1(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -105,7 +105,7 @@ Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
 Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
 Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green", 2286)]
         [TestCase(null, 70387)] // The actual answer
-        public void Part2(string input, int? expected)
+        public void Part2(string? input, int? expected)
         {
             string[] lines = input != null ? input.Split("\n") : realData;
             
@@ -175,4 +175,4 @@ Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green", 2286)]
             Console.WriteLine($"Part 2: {result}");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day03.cs b/AdventOfCode/AOC.Tests/Y2023/Day03.cs
index 2a6a41f..d60961c 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day03.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day03.cs
@@ -390,7 +390,7 @@ public class Day03
 ...$.*....
 .664.598..", 4361)]
     [TestCase(null, 550934)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -419,7 +419,7 @@ public class Day03
 ...$.*....
 .664.598..", 467835)]
     [TestCase(null, 81997870)] // The actual answer
-    public void Part2(string input, int? expected)
+    public void Part2(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day04.cs b/AdventOfCode/AOC.Tests/Y2023/Day04.cs
index c53903d..fab6392 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day04.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day04.cs
@@ -21,7 +21,7 @@ Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
 Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
 Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11", 13)]
     [TestCase(null, 17782)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -88,7 +88,7 @@ Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
 Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
 Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11", 30)]
     [TestCase(null, 8477787)] // The actual answer
-    public void Part2(string input, int? expected)
+    public void Part2(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day05.cs b/AdventOfCode/AOC.Tests/Y2023/Day05.cs
index 21298e4..09c7592 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day05.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day05.cs
@@ -112,7 +112,7 @@ humidity-to-location map:
 60 56 37
 56 93 4", 35)]
     [TestCase(null, 265018614)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
         Almanac almanac = new();
@@ -191,7 +191,7 @@ humidity-to-location map:
 60 56 37
 56 93 4", 46)]
     [TestCase(null, 63179500)] // The actual answer
-    public void Part2(string input, int? expected)
+    public void Part2(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
         Almanac almanac = new();
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day06.cs b/AdventOfCode/AOC.Tests/Y2023/Day06.cs
index 0e305b0..78dd83f 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day06.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day06.cs
@@ -17,7 +17,7 @@ public class Day06
     [TestCase(@"Time:      7  15   30
 Distance:  9  40  200", 288)]
     [TestCase(null, 1660968)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -82,7 +82,7 @@ Distance:  9  40  200", 288)]
     [TestCase(@"Time:      7  15   30
 Distance:  9  40  200", 71503)]
     [TestCase(null, 26499773)] // The actual answer
-    public void Part2(string input, int? expected)
+    public void Part2(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day07.cs b/AdventOfCode/AOC.Tests/Y2023/Day07.cs
index 6aed71d..dfb5f60 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day07.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day07.cs
@@ -20,7 +20,7 @@ KK677 28
 KTJJT 220
 QQQJA 483", 6440)]
     [TestCase(null, 247815719)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -86,7 +86,7 @@ AAAAA 61
 2JJJJ 53
 JJJJ2 41", 6839)]
     [TestCase(null, 248747492)] // The actual answer
-    public void Part2(string input, int? expected)
+    public void Part2(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
diff --git a/AdventOfCode/AOC.Tests/Y2023/Day08.cs b/AdventOfCode/AOC.Tests/Y2023/Day08.cs
index e6ac32c..4b7ed3f 100644
--- a/AdventOfCode/AOC.Tests/Y2023/Day08.cs
+++ b/AdventOfCode/AOC.Tests/Y2023/Day08.cs
@@ -29,7 +29,7 @@ AAA = (BBB, BBB)
 BBB = (AAA, ZZZ)
 ZZZ = (ZZZ, ZZZ)", 6)]
     [TestCase(null, 19199)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -89,7 +89,7 @@ ZZZ = (ZZZ, ZZZ)", 6)]
 22Z = (22B, 22B)
 XXX = (XXX, XXX)", 6)]
     [TestCase(null, 1783)] // The actual answer
-    public async Task Part2(string input, int? expected)
+    public async Task Part2(string? input, int? expected)
     {
         string[] lines = input != null ? input.Split("\n") : realData;
 
@@ -122,7 +122,7 @@ XXX = (XXX, XXX)", 6)]
             // For each location, follow the instruction
             for (int i = 0; i < currentLocations.Count; i++)
             {
-                int localI = i;  // Local copy of the loop variable
+                int localI = i; // Local copy of the loop variable
                 char instruction = instructions[instructionIndex];
                 tasks[localI] = Task.Factory.StartNew(() =>
                 {
diff --git a/AdventOfCode/DayCreator/DayX.cs b/AdventOfCode/DayCreator/DayX.cs
index b88f277..d0d32bc 100644
--- a/AdventOfCode/DayCreator/DayX.cs
+++ b/AdventOfCode/DayCreator/DayX.cs
@@ -16,7 +16,7 @@ public class DayX
 
     [TestCase("blah", 0)]
     [TestCase(null, 232)] // The actual answer
-    public void Part1(string input, int? expected)
+    public void Part1(string? input, int? expected)
     {
         string[] lines = input != null ? new[] { input } : realData;
         // string[] lines = input != null ? input.Split("\n") : realData;
@@ -31,7 +31,7 @@ public class DayX
 
     [TestCase("blah", 1)]
     [TestCase(null, 1783)] // The actual answer
-    public void Part2(string input, int? expected)
+    public void Part2(string? input, int? expected)
     {
         //string[] lines = input != null ? new[] { input } : realData;
         // string[] lines = input != null ? input.Split("\n") : realData;