Dictionary key by value: retarget net10.0, add prebuilt reverse map benchmarks (#2235)

Both projects move from net8.0 to net10.0. BenchmarkDotNet 0.15.8 and the
test packages bumped to today's newest stable.

The existing benchmark charges the two reversing methods a full build on
every call, which measures a single lookup. ReverseDictionaryLookup builds a
reverse Dictionary and a FrozenDictionary once, and two new benchmarks time
only the TryGetValue against each, with the maps built in GlobalSetup. The
four existing benchmarks are unchanged. Each new method gets the same pair of
tests the existing four have.

Author: vladimir-pecanac-main

collections-dictionary/GetDictionaryKeyByValue/GetDictionaryKeyByValue/DictionaryHelperBenchmark.cs

@@ -13,6 +13,8 @@ public class DictionaryHelperBenchmark
 
     private readonly DictionaryHelper _dictionaryHelper = new(_benchmarkDict, "NonExistentValue");
 
+    private ReverseDictionaryLookup _reverseDictionaryLookup = null!;
+
     private static Dictionary<string, string> GetDictionary()
     {
         var benchmarkDict = new Dictionary<string, string>(100000);
@@ -26,6 +28,10 @@ private static Dictionary<string, string> GetDictionary()
         return benchmarkDict;
     }
 
+    [GlobalSetup]
+    public void Setup()
+        => _reverseDictionaryLookup = new(_benchmarkDict);
+
     [Benchmark]
     public string? UseReverseDictionary()
         => _dictionaryHelper.UseReverseDictionary();
@@ -41,4 +47,12 @@ private static Dictionary<string, string> GetDictionary()
     [Benchmark]
     public string? LoopThroughTheKeys()
         => _dictionaryHelper.LoopThroughKeys();
+
+    [Benchmark]
+    public string? UsePrebuiltReverseDictionary()
+        => _reverseDictionaryLookup.GetKeyFromReverseDictionary("NonExistentValue");
+
+    [Benchmark]
+    public string? UsePrebuiltFrozenDictionary()
+        => _reverseDictionaryLookup.GetKeyFromFrozenReverseDictionary("NonExistentValue");
 }

collections-dictionary/GetDictionaryKeyByValue/GetDictionaryKeyByValue/GetDictionaryKeyByValue.csproj

@@ -2,13 +2,13 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.13.12" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.15.8" />
   </ItemGroup>
 
 </Project>

collections-dictionary/GetDictionaryKeyByValue/GetDictionaryKeyByValue/ReverseDictionaryLookup.cs

@@ -0,0 +1,36 @@
+using System.Collections.Frozen;
+
+namespace GetDictionaryKeyByValue;
+
+public class ReverseDictionaryLookup(Dictionary<string, string> dict)
+{
+    private readonly Dictionary<string, string> _reverseDict = BuildReverseDictionary(dict);
+
+    private readonly FrozenDictionary<string, string> _frozenReverseDict
+        = BuildReverseDictionary(dict).ToFrozenDictionary();
+
+    public string? GetKeyFromReverseDictionary(string value)
+    {
+        _reverseDict.TryGetValue(value, out var key);
+
+        return key;
+    }
+
+    public string? GetKeyFromFrozenReverseDictionary(string value)
+    {
+        _frozenReverseDict.TryGetValue(value, out var key);
+
+        return key;
+    }
+
+    private static Dictionary<string, string> BuildReverseDictionary(Dictionary<string, string> dict)
+    {
+        var reverseDict = new Dictionary<string, string>(dict.Count);
+        foreach (var keyValuePair in dict)
+        {
+            reverseDict.TryAdd(keyValuePair.Value, keyValuePair.Key);
+        }
+
+        return reverseDict;
+    }
+}

collections-dictionary/GetDictionaryKeyByValue/Tests/DictionaryHelperNullTest.cs

@@ -16,6 +16,8 @@ private static readonly Dictionary<string, string> _dictionary
 
     private readonly DictionaryHelper _dictionaryHelper = new(_dictionary, "NonExistentValue");
 
+    private readonly ReverseDictionaryLookup _reverseDictionaryLookup = new(_dictionary);
+
     [Fact]
     public void GivenANonExistentValue_WhenUseReverseDictionaryIsCalled_ThenReturnsNull()
     {
@@ -47,4 +49,20 @@ public void GivenANonExistentValue_WhenLoopThroughKeysIsCalled_ThenReturnsNull()
 
         Assert.Null(result);
     }
+
+    [Fact]
+    public void GivenANonExistentValue_WhenGetKeyFromReverseDictionaryIsCalled_ThenReturnsNull()
+    {
+        var result = _reverseDictionaryLookup.GetKeyFromReverseDictionary("NonExistentValue");
+
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GivenANonExistentValue_WhenGetKeyFromFrozenReverseDictionaryIsCalled_ThenReturnsNull()
+    {
+        var result = _reverseDictionaryLookup.GetKeyFromFrozenReverseDictionary("NonExistentValue");
+
+        Assert.Null(result);
+    }
 }

collections-dictionary/GetDictionaryKeyByValue/Tests/DictionaryHelperPositiveTest.cs

@@ -15,6 +15,8 @@ private static readonly Dictionary<string, string> _dictionary
 
     private readonly DictionaryHelper _dictionaryHelper = new(_dictionary, "value3");
 
+    private readonly ReverseDictionaryLookup _reverseDictionaryLookup = new(_dictionary);
+
     private static readonly string _expectedKey = "key3";
 
     [Fact]
@@ -48,4 +50,20 @@ public void GivenAnExistentValue_WhenLoopThroughKeysIsCalled_ThenReturnsTheDesir
 
         Assert.Equal(_expectedKey, result);
     }
+
+    [Fact]
+    public void GivenAnExistentValue_WhenGetKeyFromReverseDictionaryIsCalled_ThenReturnsTheDesiredKey()
+    {
+        var result = _reverseDictionaryLookup.GetKeyFromReverseDictionary("value3");
+
+        Assert.Equal(_expectedKey, result);
+    }
+
+    [Fact]
+    public void GivenAnExistentValue_WhenGetKeyFromFrozenReverseDictionaryIsCalled_ThenReturnsTheDesiredKey()
+    {
+        var result = _reverseDictionaryLookup.GetKeyFromFrozenReverseDictionary("value3");
+
+        Assert.Equal(_expectedKey, result);
+    }
 }

collections-dictionary/GetDictionaryKeyByValue/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="10.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.10.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="4.0.0" />
   </ItemGroup>
 
   <ItemGroup>