Add .NET 8.0 C# port of OpenV2G EXI codec

- Port core EXI encoding/decoding functionality to C#
- Implement V2G protocol parsing and analysis
- Add simplified decoder/encoder for roundtrip testing
- Create comprehensive error handling with EXI exceptions
- Support both byte array and file stream operations
- Include packet structure analysis for V2GTP data
- Successfully builds and runs basic functionality tests

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

TODO.md

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+# V2GDecoderC C# Porting Task List
+
+## 📋 Execution Plan
+
+### Phase 1: Setup & Analysis ✅
+- [x] Create REPORT.md with comprehensive C code analysis
+- [x] Create TODO.md with execution plan
+
+### Phase 2: .NET Core/6+ Implementation
+- [ ] Create `csharp` folder structure
+- [ ] Create `csharp\dotnet` subfolder  
+- [ ] Port core EXI codec to .NET
+- [ ] Port V2G protocol implementations (ISO1, ISO2, DIN)
+- [ ] Create test harness for .NET version
+- [ ] Test with test1.exi → test1.xml → test1.exi roundtrip
+- [ ] Validate roundtrip integrity (original vs final)
+- [ ] **Git commit** .NET version
+
+### Phase 3: .NET Framework 4.8 Implementation  
+- [ ] Create `csharp\dotnetfx` subfolder
+- [ ] Port .NET version to .NET Framework 4.8
+- [ ] Adjust for Framework-specific differences
+- [ ] Create test harness for .NET FX version
+- [ ] Test with test1.exi → test1.xml → test1.exi roundtrip
+- [ ] Validate roundtrip integrity (original vs final)
+- [ ] **Git commit** .NET Framework version
+
+### Testing Strategy
+```
+Original: test1.exi
+Step 1: Decode test1.exi → test1.xml
+Step 2: Encode test1.xml → test1_new.exi  
+Step 3: Binary compare test1.exi ≟ test1_new.exi
+Result: PASS/FAIL validation
+```
+
+### Key Porting Considerations
+- **Memory Management**: C static allocation → C# managed memory
+- **Error Handling**: C return codes → C# exceptions
+- **String Handling**: C char arrays → C# string/byte[]
+- **Buffer Operations**: C memcpy → C# Array.Copy/Buffer.BlockCopy
+- **Platform Differences**: Endianness, type sizes
+- **Security**: Address C vulnerabilities in C# implementation
+
+### Success Criteria
+1. ✅ Functional parity with C version
+2. ✅ Test roundtrip validation passes
+3. ✅ Clean separation of .NET/.NET FX versions
+4. ✅ Git commits for each major milestone
+5. ✅ Improved memory safety vs C version