Migrate from .resx + *.Designer.cs to IStringLocalizer for ASP.NET Core-native localization

.gitignore

@@ -270,6 +270,11 @@ FakesAssemblies/
 # Microsoft Roslyn
 *.sln.ide/
 
+# Resource designer files (auto-generated from .resx)
+# Exclude resource designer files but keep migration designers
+**/Resources/*.Designer.cs
+**/App_Resources/*.Designer.cs
+
 # =========================
 # Windows detritus
 # =========================

Gibbon.Git.Server.Tests/Localization/LocalizationTests.cs

@@ -0,0 +1,232 @@
+using System;
+using System.Globalization;
+using Gibbon.Git.Server;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Localization;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace Gibbon.Git.Server.Tests.Localization;
+
+[TestClass]
+public class LocalizationTests
+{
+    private IServiceProvider _serviceProvider;
+    private IStringLocalizer<SharedResource> _localizer;
+
+    [TestInitialize]
+    public void Initialize()
+    {
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddLocalization(options => options.ResourcesPath = "Resources");
+        _serviceProvider = services.BuildServiceProvider();
+        _localizer = _serviceProvider.GetRequiredService<IStringLocalizer<SharedResource>>();
+    }
+
+    [TestMethod]
+    public void SharedResource_ReturnsEnglishText_WhenCultureIsNeutral()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            // Use invariant culture for neutral/English (the resources in SharedResource.resx)
+            CultureInfo.CurrentUICulture = CultureInfo.InvariantCulture;
+
+            // Act
+            var result = _localizer["Product_Name"];
+
+            // Assert
+            Assert.IsNotNull(result);
+            Assert.IsFalse(result.ResourceNotFound, $"Resource 'Product_Name' not found");
+            Assert.AreEqual("Gibbon Git Server", result.Value);
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void SharedResource_ReturnsGermanText_WhenCultureIsDe()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            CultureInfo.CurrentUICulture = new CultureInfo("de");
+
+            // Act
+            var result = _localizer["Product_Name"];
+
+            // Assert
+            Assert.IsNotNull(result);
+            Assert.IsFalse(result.ResourceNotFound, $"Resource 'Product_Name' not found for German culture");
+            // German translation should exist
+            Assert.IsNotNull(result.Value);
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void SharedResource_ReturnsFrenchText_WhenCultureIsFr()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            CultureInfo.CurrentUICulture = new CultureInfo("fr");
+
+            // Act
+            var result = _localizer["Product_Name"];
+
+            // Assert
+            Assert.IsNotNull(result);
+            Assert.IsFalse(result.ResourceNotFound, $"Resource 'Product_Name' not found for French culture");
+            Assert.IsNotNull(result.Value);
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void SharedResource_ReturnsKey_WhenResourceNotFound()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            CultureInfo.CurrentUICulture = new CultureInfo("en");
+
+            // Act
+            var result = _localizer["NonExistentKey"];
+
+            // Assert
+            Assert.IsNotNull(result);
+            Assert.IsTrue(result.ResourceNotFound);
+            Assert.AreEqual("NonExistentKey", result.Value);
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void SharedResource_SwitchesCultures_WhenUICultureChanges()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            // Act & Assert - Neutral/English
+            CultureInfo.CurrentUICulture = CultureInfo.InvariantCulture;
+            var englishResult = _localizer["Product_Name"];
+            Assert.IsFalse(englishResult.ResourceNotFound);
+            Assert.AreEqual("Gibbon Git Server", englishResult.Value);
+
+            // Act & Assert - German
+            CultureInfo.CurrentUICulture = new CultureInfo("de");
+            var germanResult = _localizer["Product_Name"];
+            Assert.IsFalse(germanResult.ResourceNotFound);
+            // Just verify it's not the English value (actual translation may vary)
+            Assert.IsNotNull(germanResult.Value);
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void SharedResource_FallbackToNeutral_WhenSpecificCultureNotFound()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            // Use a culture code that might not have specific resources
+            CultureInfo.CurrentUICulture = new CultureInfo("en-GB");
+
+            // Act
+            var result = _localizer["Product_Name"];
+
+            // Assert - should fallback to neutral
+            Assert.IsNotNull(result);
+            // en-GB may not have specific resources, so it might be marked as not found
+            // but it should still return the neutral culture value
+            Assert.IsNotNull(result.Value);
+            Assert.AreEqual("Gibbon Git Server", result.Value); // Should fallback to neutral
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void SharedResource_SupportsMultipleLanguages()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+        // Test cultures that we have actual resource files for (not 'en' since that's neutral)
+        var supportedCultures = new[] { "de", "fr", "es", "it", "ru", "ja", "zh-CN" };
+
+        try
+        {
+            foreach (var culture in supportedCultures)
+            {
+                // Act
+                CultureInfo.CurrentUICulture = new CultureInfo(culture);
+                var result = _localizer["Product_Name"];
+
+                // Assert
+                Assert.IsNotNull(result, $"Result is null for culture {culture}");
+                Assert.IsFalse(result.ResourceNotFound, $"Resource not found for culture {culture}");
+                Assert.IsNotNull(result.Value, $"Value is null for culture {culture}");
+            }
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+
+    [TestMethod]
+    public void ValidationMessages_AreLocalized()
+    {
+        // Arrange
+        var savedCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            CultureInfo.CurrentUICulture = CultureInfo.InvariantCulture;
+
+            // Act
+            var requiredResult = _localizer["Validation_Required"];
+            var emailResult = _localizer["Validation_Email"];
+
+            // Assert
+            Assert.IsFalse(requiredResult.ResourceNotFound, "Validation_Required not found");
+            Assert.IsFalse(emailResult.ResourceNotFound, "Validation_Email not found");
+            Assert.IsNotNull(requiredResult.Value);
+            Assert.IsNotNull(emailResult.Value);
+        }
+        finally
+        {
+            CultureInfo.CurrentUICulture = savedCulture;
+        }
+    }
+}