ToDictionary in C#: .NET 10 sample with every overload shape, duplicate keys and ToLookup

csharp-linq/ToDictionaryMethodInCSharp/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>
 
@@ -10,13 +10,13 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.collector" Version="6.0.2">
+    <PackageReference Include="coverlet.collector" Version="10.1.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-    <PackageReference Include="xunit" Version="2.8.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0">
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.1">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>

csharp-linq/ToDictionaryMethodInCSharp/Tests/ToDictionaryOperationsTest.cs

@@ -10,7 +10,8 @@ private static readonly Dictionary<string, Country> _expectedCountries
             { "Egypt", new("Egypt", "Cairo", "Africa") },
             { "India", new("India", "New Delhi", "Asia") },
             { "Chile", new("Chile", "Santiago", "South America") },
-            { "Australia",  new("Australia", "Canberra", "Oceania") }
+            { "Australia",  new("Australia", "Canberra", "Oceania") },
+            { "Kenya", new("Kenya", "Nairobi", "Africa") }
         };
 
     private static readonly Dictionary<string, string> _expectedCountriesandCapitals
@@ -19,7 +20,8 @@ private static readonly Dictionary<string, string> _expectedCountriesandCapitals
             { "Egypt", "Cairo" },
             { "India", "New Delhi" },
             { "Chile", "Santiago" },
-            { "Australia", "Canberra" }
+            { "Australia", "Canberra" },
+            { "Kenya", "Nairobi" }
         };
 
     [Fact]
@@ -37,4 +39,57 @@ public void WhenCallToDictionaryWithKeysAndValuesIsCalled_ThenReturnsDictionary(
 
         Assert.True(_expectedCountriesandCapitals.OrderBy(x => x.Key).SequenceEqual(result.OrderBy(x => x.Key)));
     }
+
+    [Fact]
+    public void WhenCallToDictionaryOnKeyValuePairsIsCalled_ThenReturnsDictionary()
+    {
+        var result = ToDictionaryOperations.CallToDictionaryOnKeyValuePairs();
+
+        Assert.True(_expectedCountriesandCapitals.OrderBy(x => x.Key).SequenceEqual(result.OrderBy(x => x.Key)));
+    }
+
+    [Fact]
+    public void WhenCallToDictionaryOnTuplesIsCalled_ThenReturnsDictionary()
+    {
+        var result = ToDictionaryOperations.CallToDictionaryOnTuples();
+
+        Assert.True(_expectedCountriesandCapitals.OrderBy(x => x.Key).SequenceEqual(result.OrderBy(x => x.Key)));
+    }
+
+    [Fact]
+    public void WhenCallToDictionaryWithComparerIsCalled_ThenLookupIgnoresCase()
+    {
+        var result = ToDictionaryOperations.CallToDictionaryWithComparer();
+
+        Assert.Same(StringComparer.OrdinalIgnoreCase, result.Comparer);
+        Assert.Equal("Cairo", result["egypt"].Capital);
+    }
+
+    [Fact]
+    public void WhenCallToDictionaryWithDuplicateKeysIsCalled_ThenThrowsArgumentException()
+    {
+        var exception = Assert.Throws<ArgumentException>(
+            () => ToDictionaryOperations.CallToDictionaryWithDuplicateKeys());
+
+        Assert.Equal("An item with the same key has already been added. Key: Africa", exception.Message);
+    }
+
+    [Fact]
+    public void WhenCallToDictionaryKeepingFirstPerContinentIsCalled_ThenKeepsFirstCountry()
+    {
+        var result = ToDictionaryOperations.CallToDictionaryKeepingFirstPerContinent();
+
+        Assert.Equal(4, result.Count);
+        Assert.Equal("Egypt", result["Africa"].Name);
+    }
+
+    [Fact]
+    public void WhenCallToLookupOnContinentsIsCalled_ThenGroupsCountriesPerContinent()
+    {
+        var result = ToDictionaryOperations.CallToLookupOnContinents();
+
+        Assert.Equal(4, result.Count);
+        Assert.Equal(2, result["Africa"].Count());
+        Assert.Empty(result["Antarctica"]);
+    }
 }

csharp-linq/ToDictionaryMethodInCSharp/ToDictionaryMethodInCSharp/ToDictionaryMethodInCSharp.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>
   </PropertyGroup>

csharp-linq/ToDictionaryMethodInCSharp/ToDictionaryMethodInCSharp/ToDictionaryOperations.cs

@@ -7,12 +7,38 @@ private static readonly List<Country> _countries
             new("Egypt", "Cairo", "Africa"),
             new("India", "New Delhi", "Asia"),
             new("Chile", "Santiago", "South America"),
-            new("Australia", "Canberra", "Oceania")
+            new("Australia", "Canberra", "Oceania"),
+            new("Kenya", "Nairobi", "Africa")
           ];
 
     public static Dictionary<string, Country> CallToDictionaryWithKeysOnly()
         => _countries.ToDictionary(c => c.Name);
 
     public static Dictionary<string, string> CallToDictionaryWithKeysAndValues()
         => _countries.ToDictionary(c => c.Name, c => c.Capital);
+
+    public static Dictionary<string, string> CallToDictionaryOnKeyValuePairs()
+        => _countries
+            .Select(c => new KeyValuePair<string, string>(c.Name, c.Capital))
+            .ToDictionary();
+
+    public static Dictionary<string, string> CallToDictionaryOnTuples()
+        => _countries
+            .Select(c => (c.Name, c.Capital))
+            .ToDictionary();
+
+    public static Dictionary<string, Country> CallToDictionaryWithComparer()
+        => _countries.ToDictionary(c => c.Name, StringComparer.OrdinalIgnoreCase);
+
+    // Throws: two countries share the continent "Africa"
+    public static Dictionary<string, Country> CallToDictionaryWithDuplicateKeys()
+        => _countries.ToDictionary(c => c.Continent);
+
+    public static Dictionary<string, Country> CallToDictionaryKeepingFirstPerContinent()
+        => _countries
+            .DistinctBy(c => c.Continent)
+            .ToDictionary(c => c.Continent);
+
+    public static ILookup<string, Country> CallToLookupOnContinents()
+        => _countries.ToLookup(c => c.Continent);
 }