成本管理系统性能与安全设计：百万级数据效率优化方案 + 数据加密策略

// 使用Entity Framework Core进行分页查询的示例
public async Task<>> GetPagedCostRecordsAsync(int pageIndex, int pageSize)
{
    var query = _context.CostRecords
        .Where(r => r.IsActive)
        .OrderBy(r => r.RecordDate);
        
    return await PagedList.CreateAsync(query, pageIndex, pageSize);
}

// 高效查询实现类
public class PagedList : List
{
    public int CurrentPage { get; private set; }
    public int TotalPages { get; private set; }
    public int PageSize { get; private set; }
    public int TotalCount { get; private set; }

    public PagedList(List items, int count, int pageIndex, int pageSize)
    {
        TotalCount = count;
        PageSize = pageSize;
        CurrentPage = pageIndex;
        TotalPages = (int)Math.Ceiling(count / (double)pageSize);
        AddRange(items);
    }

    public static async Task<>> CreateAsync(IQueryable source, int pageIndex, int pageSize)
    {
        var count = await source.CountAsync();
        var items = await source.Skip((pageIndex - 1) * pageSize).Take(pageSize).ToListAsync();
        return new PagedList(items, count, pageIndex, pageSize);
    }
}

// 使用AES加密算法保护敏感数据
public class DataEncryptionService
{
    private readonly byte[] _key;
    private readonly byte[] _iv;

    public DataEncryptionService(IConfiguration configuration)
    {
        _key = Convert.FromBase64String(configuration["Encryption:Key"]);
        _iv = Convert.FromBase64String(configuration["Encryption:IV"]);
    }

    public string Encrypt(string plainText)
    {
        using var aes = Aes.Create();
        aes.Key = _key;
        aes.IV = _iv;

        var encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
        using var memoryStream = new MemoryStream();
        using var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);
        using (var streamWriter = new StreamWriter(cryptoStream))
        {
            streamWriter.Write(plainText);
        }
        
        return Convert.ToBase64String(memoryStream.ToArray());
    }

    public string Decrypt(string cipherText)
    {
        var buffer = Convert.FromBase64String(cipherText);
        using var aes = Aes.Create();
        aes.Key = _key;
        aes.IV = _iv;

        var decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
        using var memoryStream = new MemoryStream(buffer);
        using var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
        using var streamReader = new StreamReader(cryptoStream);
        return streamReader.ReadToEnd();
    }
}