diff --git a/csharp-linq/LookupInCSharp/LookupInCSharp/LookupInCSharp.csproj b/csharp-linq/LookupInCSharp/LookupInCSharp/LookupInCSharp.csproj
index 405f6f99f7..eb9c09aae9 100644
--- a/csharp-linq/LookupInCSharp/LookupInCSharp/LookupInCSharp.csproj
+++ b/csharp-linq/LookupInCSharp/LookupInCSharp/LookupInCSharp.csproj
@@ -2,7 +2,7 @@
 
 	<PropertyGroup>
 		<OutputType>Library</OutputType>
-		<TargetFramework>net8.0</TargetFramework>
+		<TargetFramework>net10.0</TargetFramework>
 		<ImplicitUsings>enable</ImplicitUsings>
 		<Nullable>enable</Nullable>
 	</PropertyGroup>
diff --git a/csharp-linq/LookupInCSharp/LookupInCSharp/LookupOperations.cs b/csharp-linq/LookupInCSharp/LookupInCSharp/LookupOperations.cs
index b9917d20cd..4fddb78b14 100644
--- a/csharp-linq/LookupInCSharp/LookupInCSharp/LookupOperations.cs
+++ b/csharp-linq/LookupInCSharp/LookupInCSharp/LookupOperations.cs
@@ -30,4 +30,17 @@ public static bool SearchForKeyInLookup(string key)
 
     public static int GetLookupCount()
         => _lookup.Count;
-}
\ No newline at end of file
+
+    public static (int FromGroupBy, int FromLookup) CountValuesAfterSourceChanges(
+        string key, Student newStudent)
+    {
+        List<Student> students = [.. _students];
+
+        var grouped = students.GroupBy(s => s.Name, s => s.Course);
+        var lookup = students.ToLookup(s => s.Name, s => s.Course);
+
+        students.Add(newStudent);
+
+        return (grouped.Single(g => g.Key == key).Count(), lookup[key].Count());
+    }
+}
diff --git a/csharp-linq/LookupInCSharp/Tests/LookupOperationsTest.cs b/csharp-linq/LookupInCSharp/Tests/LookupOperationsTest.cs
index 89fdf218ea..b8dcc8ae83 100644
--- a/csharp-linq/LookupInCSharp/Tests/LookupOperationsTest.cs
+++ b/csharp-linq/LookupInCSharp/Tests/LookupOperationsTest.cs
@@ -75,4 +75,22 @@ public void WhenGetLookupCountIsCalled_ThenReturnsTheLookupCount()
 
         Assert.Equal(3, count);
     }
-}
\ No newline at end of file
+
+    [Fact]
+    public void GivenKeyThatDoesNotExist_WhenRetrieveValuesOfAKeyFromLookupIsCalled_ThenReturnsEmpty()
+    {
+        var values = LookupOperations.RetrieveValuesOfAKeyFromLookup("Michael Sorla");
+
+        Assert.Empty(values);
+    }
+
+    [Fact]
+    public void GivenSourceChangesAfterTheCall_WhenCountValuesAfterSourceChangesIsCalled_ThenOnlyGroupBySeesTheChange()
+    {
+        var (fromGroupBy, fromLookup) = LookupOperations.CountValuesAfterSourceChanges(
+            "Kate Green", new Student("Kate Green", "Taxation"));
+
+        Assert.Equal(2, fromGroupBy);
+        Assert.Equal(1, fromLookup);
+    }
+}
diff --git a/csharp-linq/LookupInCSharp/Tests/Tests.csproj b/csharp-linq/LookupInCSharp/Tests/Tests.csproj
index 5c9a7737e2..2b987baa22 100644
--- a/csharp-linq/LookupInCSharp/Tests/Tests.csproj
+++ b/csharp-linq/LookupInCSharp/Tests/Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
 
@@ -10,10 +10,10 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.collector" Version="6.0.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageReference Include="xunit" Version="2.5.3" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
+    <PackageReference Include="coverlet.collector" Version="10.1.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.11.0" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.1" />
   </ItemGroup>
 
   <ItemGroup>