Add C# implementation

.github/workflows/test.yml

@@ -61,3 +61,30 @@ jobs:
     - name: Run example
       working-directory: ./js
       run: npm run example
+
+  test-csharp:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up .NET
+      uses: actions/setup-dotnet@v4
+      with:
+        dotnet-version: '8.0.x'
+
+    - name: Restore dependencies
+      working-directory: ./csharp
+      run: dotnet restore
+
+    - name: Build
+      working-directory: ./csharp
+      run: dotnet build --no-restore
+
+    - name: Run tests
+      working-directory: ./csharp
+      run: dotnet test --no-build --verbosity normal
+
+    - name: Run example
+      working-directory: ./csharp
+      run: dotnet run --project examples/BasicUsage.csproj

README.md

@@ -3,23 +3,25 @@
 [![Tests](https://github.com/link-foundation/lino-objects-codec/actions/workflows/test.yml/badge.svg)](https://github.com/link-foundation/lino-objects-codec/actions/workflows/test.yml)
 [![Python Version](https://img.shields.io/pypi/pyversions/lino-objects-codec.svg)](https://pypi.org/project/lino-objects-codec/)
 
-Universal serialization library to encode/decode objects to/from Links Notation format. Available in both **Python** and **JavaScript** with identical functionality and API design.
+Universal serialization library to encode/decode objects to/from Links Notation format. Available in **Python**, **JavaScript**, and **C#** with identical functionality and API design.
 
 ## 🌍 Multi-Language Support
 
 This library provides universal serialization and deserialization with built-in support for circular references and complex object graphs in:
 
 - **[Python](python/)** - Full implementation for Python 3.8+
 - **[JavaScript](js/)** - Full implementation for Node.js 18+
+- **[C#](csharp/)** - Full implementation for .NET 8.0+
 
-Both implementations share the same design philosophy and provide feature parity.
+All implementations share the same design philosophy and provide feature parity.
 
 ## Features
 
 - **Universal Serialization**: Encode objects to Links Notation format
 - **Type Support**: Handle all common types in each language:
   - **Python**: `None`, `bool`, `int`, `float`, `str`, `list`, `dict`
   - **JavaScript**: `null`, `undefined`, `boolean`, `number`, `string`, `Array`, `Object`
+  - **C#**: `null`, `bool`, `int`, `long`, `float`, `double`, `string`, `List<object?>`, `Dictionary<string, object?>`
   - Special float/number values: `NaN`, `Infinity`, `-Infinity`
 - **Circular References**: Automatically detect and preserve circular references
 - **Object Identity**: Maintain object identity for shared references
@@ -63,6 +65,27 @@ const decoded = decode(encoded);
 console.log(JSON.stringify(decoded) === JSON.stringify(data)); // true
 ```
 
+### C#
+
+```bash
+dotnet add package Lino.Objects.Codec
+```
+
+```csharp
+using Lino.Objects.Codec;
+
+// Encode and decode
+var data = new Dictionary<string, object?>
+{
+    { "name", "Alice" },
+    { "age", 30 },
+    { "active", true }
+};
+var encoded = Codec.Encode(data);
+var decoded = Codec.Decode(encoded) as Dictionary<string, object?>;
+Console.WriteLine(decoded?["name"]); // Alice
+```
+
 ## Repository Structure
 
 ```
@@ -77,6 +100,11 @@ console.log(JSON.stringify(decoded) === JSON.stringify(data)); // true
 │   ├── tests/       # Test suite
 │   ├── examples/    # Usage examples
 │   └── README.md    # JavaScript-specific docs
+├── csharp/          # C# implementation
+│   ├── src/         # Source code
+│   ├── tests/       # Test suite
+│   ├── examples/    # Usage examples
+│   └── README.md    # C#-specific docs
 └── README.md        # This file
 ```
 
@@ -86,10 +114,11 @@ For detailed documentation, API reference, and examples, see:
 
 - **[Python Documentation](python/README.md)**
 - **[JavaScript Documentation](js/README.md)**
+- **[C# Documentation](csharp/README.md)**
 
 ## Usage Examples
 
-Both implementations support the same features with language-appropriate syntax:
+All implementations support the same features with language-appropriate syntax:
 
 ### Circular References
 
@@ -115,6 +144,17 @@ const decoded = decode(encode(arr));
 console.log(decoded[3] === decoded); // true - Reference preserved
 ```
 
+**C#:**
+```csharp
+using Lino.Objects.Codec;
+
+// Self-referencing list
+var lst = new List<object?>();
+lst.Add(lst);
+var decoded = Codec.Decode(Codec.Encode(lst)) as List<object?>;
+Console.WriteLine(ReferenceEquals(decoded, decoded?[0])); // True - Reference preserved
+```
+
 ### Complex Nested Structures
 
 **Python:**
@@ -141,6 +181,22 @@ const data = {
 console.log(JSON.stringify(decode(encode(data))) === JSON.stringify(data));
 ```
 
+**C#:**
+```csharp
+var data = new Dictionary<string, object?>
+{
+    {
+        "users", new List<object?>
+        {
+            new Dictionary<string, object?> { { "id", 1 }, { "name", "Alice" } },
+            new Dictionary<string, object?> { { "id", 2 }, { "name", "Bob" } }
+        }
+    },
+    { "metadata", new Dictionary<string, object?> { { "version", 1 }, { "count", 2 } } }
+};
+var decoded = Codec.Decode(Codec.Encode(data));
+```
+
 ## How It Works
 
 The library uses the [links-notation](https://github.com/link-foundation/links-notation) format as the serialization target. Each object is encoded as a Link with type information:
@@ -181,6 +237,15 @@ npm test
 npm run example
 ```
 
+### C#
+
+```bash
+cd csharp
+dotnet build
+dotnet test
+dotnet run --project examples/BasicUsage.csproj
+```
+
 ## Contributing
 
 Contributions are welcome! Please feel free to submit a Pull Request.
@@ -203,6 +268,7 @@ This project is licensed under the Unlicense - see the [LICENSE](LICENSE) file f
 - [Links Notation Specification](https://github.com/link-foundation/links-notation)
 - [PyPI Package](https://pypi.org/project/lino-objects-codec/) (Python)
 - [npm Package](https://www.npmjs.com/package/lino-objects-codec/) (JavaScript)
+- [NuGet Package](https://www.nuget.org/packages/Lino.Objects.Codec/) (C#)
 
 ## Acknowledgments
 

csharp/.gitignore

@@ -0,0 +1,55 @@
+# Build results
+[Dd]ebug/
+[Dd]ebugPublic/
+[Rr]elease/
+[Rr]eleases/
+x64/
+x86/
+[Ww][Ii][Nn]32/
+[Aa][Rr][Mm]/
+[Aa][Rr][Mm]64/
+bld/
+[Bb]in/
+[Oo]bj/
+[Ll]og/
+[Ll]ogs/
+
+# Visual Studio
+.vs/
+*.user
+*.userosscache
+*.suo
+*.sln.docstates
+
+# NuGet
+*.nupkg
+*.snupkg
+.nuget/
+packages/
+**/packages.lock.json
+
+# Test results
+[Tt]est[Rr]esult*/
+[Tt]est[Rr]un*.trx
+*.coverage
+*.coveragexml
+*.dotCover
+
+# Build outputs
+*.dll
+*.exe
+*.pdb
+!TestResults/
+
+# User-specific files
+*.rsuser
+*.suo
+*.user
+*.sln.docstates
+
+# JetBrains Rider
+.idea/
+*.sln.iml
+
+# macOS
+.DS_Store

csharp/Lino.Objects.Codec.sln

@@ -0,0 +1,25 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lino.Objects.Codec", "src\Lino.Objects.Codec\Lino.Objects.Codec.csproj", "{A1B2C3D4-E5F6-7890-ABCD-EF1234567890}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lino.Objects.Codec.Tests", "tests\Lino.Objects.Codec.Tests\Lino.Objects.Codec.Tests.csproj", "{B2C3D4E5-F6A7-8901-BCDE-F12345678901}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{A1B2C3D4-E5F6-7890-ABCD-EF1234567890}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A1B2C3D4-E5F6-7890-ABCD-EF1234567890}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A1B2C3D4-E5F6-7890-ABCD-EF1234567890}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A1B2C3D4-E5F6-7890-ABCD-EF1234567890}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B2C3D4E5-F6A7-8901-BCDE-F12345678901}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B2C3D4E5-F6A7-8901-BCDE-F12345678901}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B2C3D4E5-F6A7-8901-BCDE-F12345678901}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B2C3D4E5-F6A7-8901-BCDE-F12345678901}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal