Merge pull request #33 from jonsagara/feature/emptydict

Added an EmptyDictionary class. Upgraded SE.Redis and NodaTime.

Author: jonsagara

Directory.Build.props

@@ -7,7 +7,7 @@
 		<LangVersion>13.0</LangVersion>
 
 		<!-- NuGet -->
-		<Version>3.1.5</Version>
+		<Version>3.1.6</Version>
 		<AssemblyVersion>3.1.0</AssemblyVersion>
 		<FileVersion>3.1.0</FileVersion>
 		<Authors>Jon Sagara</Authors>

src/Sagara.Core.Caching/Sagara.Core.Caching.csproj

@@ -37,7 +37,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<PackageReference Include="StackExchange.Redis" Version="2.8.22" />
+		<PackageReference Include="StackExchange.Redis" Version="2.8.24" />
 	</ItemGroup>
 
 	<ItemGroup>

src/Sagara.Core/Collections/EmptyDictionary.cs

@@ -0,0 +1,65 @@
+using System.Collections;
+using System.Collections.ObjectModel;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Sagara.Core.Collections;
+
+/// <summary>
+/// Provides a cached, read-only instance for the specified key and value types.
+/// </summary>
+/// <remarks>
+/// <para>We're implementing <see cref="IReadOnlyDictionary{TKey, TValue}"/> to get a true read-only dictionary without
+/// risking various extension methods leading to runtime exceptions. For example, <see cref="ReadOnlyDictionary{TKey, TValue}"/>
+/// implements <see cref="IDictionary{TKey, TValue}"/>, which in turn lights up the <see cref="CollectionExtensions.TryAdd{TKey, TValue}(IDictionary{TKey, TValue}, TKey, TValue)"/>
+/// extension method that will throw at runtime if called on a <see cref="ReadOnlyDictionary{TKey, TValue}"/>.</para>
+/// </remarks>
+/// <typeparam name="TKey">The type of keys in the read-only dictionary.</typeparam>
+/// <typeparam name="TValue">The type of values in the read-only dictionary.</typeparam>
+public sealed class EmptyDictionary<TKey, TValue> : IReadOnlyDictionary<TKey, TValue>
+    where TKey : notnull
+{
+    /// <summary>
+    /// The one and only instance of <see cref="EmptyDictionary{TKey, TValue}"/> for this key/value type pair.
+    /// </summary>
+    public static readonly IReadOnlyDictionary<TKey, TValue> Instance = ReadOnlyDictionary<TKey, TValue>.Empty;
+
+    /// <summary>
+    /// Don't let callers create their own instances.
+    /// </summary>
+    private EmptyDictionary()
+    {
+        // Intentionally blank.
+    }
+
+    /// <inheritdoc/>
+    public TValue this[TKey key]
+        => Instance[key];
+
+    /// <inheritdoc/>
+    public IEnumerable<TKey> Keys
+        => Instance.Keys;
+
+    /// <inheritdoc/>
+    public IEnumerable<TValue> Values
+        => Instance.Values;
+
+    /// <inheritdoc/>
+    public int Count
+        => Instance.Count;
+
+    /// <inheritdoc/>
+    public bool ContainsKey(TKey key)
+        => Instance.ContainsKey(key);
+
+    /// <inheritdoc/>
+    public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
+        => Instance.GetEnumerator();
+
+    /// <inheritdoc/>
+    public bool TryGetValue(TKey key, [MaybeNullWhen(false)] out TValue value)
+        => Instance.TryGetValue(key, out value);
+
+    /// <inheritdoc/>
+    IEnumerator IEnumerable.GetEnumerator()
+        => ((IEnumerable)Instance).GetEnumerator();
+}

src/Sagara.Core/Sagara.Core.csproj

@@ -29,7 +29,7 @@
 
 	<ItemGroup>
 		<PackageReference Include="Microsoft.IO.RecyclableMemoryStream" Version="3.0.1" />
-		<PackageReference Include="NodaTime" Version="3.2.0" />
+		<PackageReference Include="NodaTime" Version="3.2.1" />
 	</ItemGroup>
 
 	<ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">