git-hardening/.crosslink/rules/csharp.md

C# Best Practices

Code Style

• Follow .NET naming conventions (PascalCase for public, camelCase for private)
• Use var when type is obvious from right side
• Use expression-bodied members for simple methods
• Enable nullable reference types

// GOOD: Modern C# style
public class UserService
{
    private readonly IUserRepository _repository;

    public UserService(IUserRepository repository)
        => _repository = repository;

    public async Task<User?> GetUserAsync(string id)
        => await _repository.FindByIdAsync(id);
}

Error Handling

• Use specific exception types
• Never catch and swallow exceptions silently
• Use try-finally or using for cleanup

// GOOD: Proper async error handling
public async Task<Result<User>> GetUserAsync(string id)
{
    try
    {
        var user = await _repository.FindByIdAsync(id);
        return user is null
            ? Result<User>.NotFound()
            : Result<User>.Ok(user);
    }
    catch (DbException ex)
    {
        _logger.LogError(ex, "Database error fetching user {Id}", id);
        throw;
    }
}

Security

• Use parameterized queries (never string interpolation for SQL)
• Validate all input with data annotations or FluentValidation
• Use ASP.NET's built-in anti-forgery tokens
• Store secrets in Azure Key Vault or similar