exercism · ErikSchierboom · Feb 18, 2025 · Feb 17, 2025 · Feb 17, 2025 · Feb 17, 2025
diff --git a/bin/add-practice-exercise.ps1 b/bin/add-practice-exercise.ps1
@@ -39,7 +39,6 @@ $project = "${exerciseDir}/${ExerciseName}.csproj"
 [xml]$projectXml = Get-Content "${project}"
 $projectXml.Project.RemoveChild($projectXml.Project.ItemGroup[1])
 $projectXml.Project.PropertyGroup.RemoveChild($projectXml.Project.PropertyGroup.SelectSingleNode("ImplicitUsings"))
-$projectXml.Project.PropertyGroup.RemoveChild($projectXml.Project.PropertyGroup.SelectSingleNode("Nullable"))
 $projectXml.Save("${project}")
 
 # Update project packages

diff --git a/exercises/concept/annalyns-infiltration/AnnalynsInfiltration.csproj b/exercises/concept/annalyns-infiltration/AnnalynsInfiltration.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/attack-of-the-trolls/AttackOfTheTrolls.csproj b/exercises/concept/attack-of-the-trolls/AttackOfTheTrolls.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/authentication-system/AuthenticationSystem.csproj b/exercises/concept/authentication-system/AuthenticationSystem.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/beauty-salon-goes-global/BeautySalonGoesGlobal.csproj b/exercises/concept/beauty-salon-goes-global/BeautySalonGoesGlobal.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/bird-watcher/BirdWatcher.csproj b/exercises/concept/bird-watcher/BirdWatcher.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/booking-up-for-beauty/BookingUpForBeauty.csproj b/exercises/concept/booking-up-for-beauty/BookingUpForBeauty.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/building-telemetry/BuildingTelemetry.csproj b/exercises/concept/building-telemetry/BuildingTelemetry.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/calculator-conundrum/.meta/Exemplar.cs b/exercises/concept/calculator-conundrum/.meta/Exemplar.cs
@@ -2,7 +2,7 @@
 
 public static class SimpleCalculator
 {
-    public static string Calculate(int operand1, int operand2, string operation)
+    public static string Calculate(int operand1, int operand2, string? operation)
     {
         int result;
         try

diff --git a/exercises/concept/calculator-conundrum/CalculatorConundrum.cs b/exercises/concept/calculator-conundrum/CalculatorConundrum.cs
@@ -2,7 +2,7 @@
 
 public static class SimpleCalculator
 {
-    public static string Calculate(int operand1, int operand2, string operation)
+    public static string Calculate(int operand1, int operand2, string? operation)
     {
         throw new NotImplementedException("Please implement the SimpleCalculator.Calculate() method");
     }

diff --git a/exercises/concept/calculator-conundrum/CalculatorConundrum.csproj b/exercises/concept/calculator-conundrum/CalculatorConundrum.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/cars-assemble/CarsAssemble.csproj b/exercises/concept/cars-assemble/CarsAssemble.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/developer-privileges/.meta/Exemplar.cs b/exercises/concept/developer-privileges/.meta/Exemplar.cs
@@ -44,14 +44,14 @@ public class Authenticator
 //**** please do not modify the FacialFeatures class ****
 public class FacialFeatures
 {
-    public string EyeColor { get; set; }
-    public decimal PhiltrumWidth { get; set; }
+    public required string EyeColor { get; set; }
+    public required decimal PhiltrumWidth { get; set; }
 }
 
 //**** please do not modify the Identity class ****
 public class Identity
 {
-    public string Email { get; set; }
-    public FacialFeatures FacialFeatures { get; set; }
-    public IList<string> NameAndAddress { get; set; }
+    public required string Email { get; set; }
+    public required FacialFeatures FacialFeatures { get; set; }
+    public required IList<string> NameAndAddress { get; set; }
 }
diff --git a/exercises/concept/developer-privileges/DeveloperPrivileges.cs b/exercises/concept/developer-privileges/DeveloperPrivileges.cs
@@ -13,14 +13,14 @@ public class Authenticator
 //**** please do not modify the FacialFeatures class ****
 public class FacialFeatures
 {
-    public string EyeColor { get; set; }
-    public decimal PhiltrumWidth { get; set; }
+    public required string EyeColor { get; set; }
+    public required decimal PhiltrumWidth { get; set; }
 }
 
 //**** please do not modify the Identity class ****
 public class Identity
 {
-    public string Email { get; set; }
-    public FacialFeatures FacialFeatures { get; set; }
-    public IList<string> NameAndAddress { get; set; }
+    public required string Email { get; set; }
+    public required FacialFeatures FacialFeatures { get; set; }
+    public required IList<string> NameAndAddress { get; set; }
 }
diff --git a/exercises/concept/developer-privileges/DeveloperPrivileges.csproj b/exercises/concept/developer-privileges/DeveloperPrivileges.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/elons-toys/ElonsToys.csproj b/exercises/concept/elons-toys/ElonsToys.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/faceid-2/.meta/Exemplar.cs b/exercises/concept/faceid-2/.meta/Exemplar.cs
@@ -17,7 +17,7 @@ protected bool Equals(FacialFeatures other)
         return EyeColor == other.EyeColor && PhiltrumWidth.Equals(other.PhiltrumWidth);
     }
 
-    public override bool Equals(object obj)
+    public override bool Equals(object? obj)
     {
         if (ReferenceEquals(null, obj)) return false;
         if (ReferenceEquals(this, obj)) return true;
@@ -47,7 +47,7 @@ protected bool Equals(Identity other)
         return Email == other.Email && Equals(FacialFeatures, other.FacialFeatures);
     }
 
-    public override bool Equals(object obj)
+    public override bool Equals(object? obj)
     {
         if (ReferenceEquals(null, obj)) return false;
         if (ReferenceEquals(this, obj)) return true;

diff --git a/exercises/concept/faceid-2/Faceid2.csproj b/exercises/concept/faceid-2/Faceid2.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/high-school-sweethearts/HighSchoolSweethearts.csproj b/exercises/concept/high-school-sweethearts/HighSchoolSweethearts.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/hyper-optimized-telemetry/HyperOptimizedTelemetry.csproj b/exercises/concept/hyper-optimized-telemetry/HyperOptimizedTelemetry.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/hyperia-forex/HyperiaForex.csproj b/exercises/concept/hyperia-forex/HyperiaForex.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/hyperinflation-hits-hyperia/HyperinflationHitsHyperia.csproj b/exercises/concept/hyperinflation-hits-hyperia/HyperinflationHitsHyperia.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/instruments-of-texas/.meta/Exemplar.cs b/exercises/concept/instruments-of-texas/.meta/Exemplar.cs
@@ -30,11 +30,11 @@ public string TestMultiplication(int x, int y)
         }
         catch (CalculationException cex) when (cex.Operand1 < 0 && cex.Operand2 < 0)
         {
-            return "Multiply failed for negative operands. " + cex.InnerException.Message;
+            return "Multiply failed for negative operands. " + cex.InnerException!.Message;
         }
         catch (CalculationException cex)
         {
-            return "Multiply failed for mixed or positive operands. " + cex.InnerException.Message;
+            return "Multiply failed for mixed or positive operands. " + cex.InnerException!.Message;
         }
     }
 

diff --git a/exercises/concept/instruments-of-texas/InstrumentsOfTexas.csproj b/exercises/concept/instruments-of-texas/InstrumentsOfTexas.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/interest-is-interesting/InterestIsInteresting.csproj b/exercises/concept/interest-is-interesting/InterestIsInteresting.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/international-calling-connoisseur/InternationalCallingConnoisseur.csproj b/exercises/concept/international-calling-connoisseur/InternationalCallingConnoisseur.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/land-grab-in-space/LandGrabInSpace.csproj b/exercises/concept/land-grab-in-space/LandGrabInSpace.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/land-grab-in-space/LandGrabInSpaceTests.cs b/exercises/concept/land-grab-in-space/LandGrabInSpaceTests.cs
@@ -74,16 +74,13 @@ public void GetLongestSideReverseInsertionOrder()
     private Plot CreatePlot(Coord coord1, Coord coord2, Coord coord3, Coord coord4)
     {
         Type plotType = typeof(Plot);
-        Type[] types = new Type[] { typeof(Coord), typeof(Coord), typeof(Coord), typeof(Coord) };
-        ConstructorInfo constructorInfoObj = plotType.GetConstructor(types);
+        Type[] types = [typeof(Coord), typeof(Coord), typeof(Coord), typeof(Coord)];
+        ConstructorInfo? constructorInfoObj = plotType.GetConstructor(types);
         if (constructorInfoObj != null)
         {
-            return (Plot)constructorInfoObj.Invoke(new object[] { coord1, coord2, coord3, coord4 });
+            return (Plot)constructorInfoObj.Invoke([coord1, coord2, coord3, coord4]);
         }
 
-        else
-        {
-            throw new InvalidOperationException("You need to implement a constructor for the struct Plot.  The constructor must take 4 co-ordinates.  No such constructor can be found.");
-        }
+        throw new InvalidOperationException("You need to implement a constructor for the struct Plot.  The constructor must take 4 co-ordinates.  No such constructor can be found.");
     }
 }
diff --git a/exercises/concept/log-analysis/LogAnalysis.csproj b/exercises/concept/log-analysis/LogAnalysis.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/log-levels/LogLevels.csproj b/exercises/concept/log-levels/LogLevels.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/logs-logs-logs/LogsLogsLogs.csproj b/exercises/concept/logs-logs-logs/LogsLogsLogs.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/lucians-luscious-lasagna/LuciansLusciousLasagna.csproj b/exercises/concept/lucians-luscious-lasagna/LuciansLusciousLasagna.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/need-for-speed/NeedForSpeed.csproj b/exercises/concept/need-for-speed/NeedForSpeed.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/object-relational-mapping/ObjectRelationalMapping.csproj b/exercises/concept/object-relational-mapping/ObjectRelationalMapping.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/orm-in-one-go/OrmInOneGo.csproj b/exercises/concept/orm-in-one-go/OrmInOneGo.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/parsing-log-files/ParsingLogFiles.csproj b/exercises/concept/parsing-log-files/ParsingLogFiles.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/phone-number-analysis/PhoneNumberAnalysis.csproj b/exercises/concept/phone-number-analysis/PhoneNumberAnalysis.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/red-vs-blue-darwin-style/RedVsBlueDarwinStyle.csproj b/exercises/concept/red-vs-blue-darwin-style/RedVsBlueDarwinStyle.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/remote-control-cleanup/.meta/Exemplar.cs b/exercises/concept/remote-control-cleanup/.meta/Exemplar.cs
@@ -1,3 +1,5 @@
+#pragma warning disable CS8618
+
 public class RemoteControlCar
 {
     private enum SpeedUnits
@@ -95,3 +97,5 @@ private void SetSpeed(Speed speed)
         currentSpeed = speed;
     }
 }
+
+#pragma warning restore CS8618
diff --git a/exercises/concept/remote-control-cleanup/RemoteControlCleanup.csproj b/exercises/concept/remote-control-cleanup/RemoteControlCleanup.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
     <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 

diff --git a/exercises/concept/remote-control-competition/.meta/Exemplar.cs b/exercises/concept/remote-control-competition/.meta/Exemplar.cs
@@ -17,7 +17,7 @@ public void Drive()
         DistanceTravelled += 10;
     }
 
-    public int CompareTo(ProductionRemoteControlCar other)
+    public int CompareTo(ProductionRemoteControlCar? other)
     {
         if (ReferenceEquals(this, other)) return 0;
         if (ReferenceEquals(null, other)) return 1;