Question

我大约有15个实体，必须为其获取 id 和 name 属性。首先，我检查是否可以从本地缓存中提取属性。如果没有，那么我将通过代码从数据库中获取它们并保存在缓存中。

这是我针对两个实体的代码：

public class GetParamsService : IGetParamsService
{
    private readonly IMemoryCache _cache;
    private readonly MemoryCacheEntryOptions _cacheOptions;
    private readonly IDealTypeRepository _dealTypeRepository;
    private readonly ICurrencyRepository _currencyRepository;      

    public GetParamsService(IMemoryCache memoryCache, 
        IDealTypeRepository dealTypeRepository,
        ICurrencyRepository currencyRepository)
    {
        _cache = memoryCache;
        _cacheOptions = new MemoryCacheEntryOptions()
            .SetSlidingExpiration(TimeSpan.FromHours(2));

        _dealTypeRepository = dealTypeRepository;
        _currencyRepository = currencyRepository;
    }

    public async Task<(int idDealType, string dealTypeName)> GetDealTypeParams(
        string dealTypeCode)
    {
        if (!_cache.TryGetValue(CacheKeys.IdDealType, out int idDealType)
            | !_cache.TryGetValue(CacheKeys.DealTypeName, out string dealTypeName))
        {
            var dealType = await _dealTypeRepository
                .Get(x => x.Code == dealTypeCode, dealTypeCode);

            idDealType = dealType.IdDealType;
            dealTypeName = dealType.Name;

            _cache.Set(CacheKeys.IdDealType, idDealType, _cacheOptions);
            _cache.Set(CacheKeys.DealTypeName, dealTypeName, _cacheOptions);
        }

        return (idDealType, dealTypeName);
    }

    public async Task<(int idCurrency, string currencyName)> GetCurrencyParams(
        string currencyCode)
    {
        if (!_cache.TryGetValue(CacheKeys.IdCurrency, out int idCurrency)
            | !_cache.TryGetValue(CacheKeys.CurrencyName, out string currencyName))
        {
            var currency = await _currencyRepository
                .Get(x => x.Code == currencyCode, currencyCode);

            idCurrency = currency.IdCurrency;
            currencyName = currency.Name;

            _cache.Set(CacheKeys.IdCurrency, idCurrency, _cacheOptions);
            _cache.Set(CacheKeys.CurrencyName, currencyName, _cacheOptions);
        }

        return (idCurrency, currencyName);
    }
}

因此，方法 GetDealTypeParams 和 GetCurrencyParams 相同，我想使一个通用方法代替许多类似方法。我想这很有道理。

问题是我不知道如何在CacheKeys类中获取“给定实体的正确属性”：

public static class CacheKeys
{
    public static string IdDealType => "_IdDealType";

    public static string DealTypeName => "_DealTypeName";

    public static string IdCurrency => "_IdCurrency";

    public static string CurrencyName => "_CurrencyName";

    // ...

}

每个存储库都是使用 Get 方法从GenericRepository继承的：

public class DealTypeRepository : GenericRepository<DealTypeEntity>, IDealTypeRepository
{       
    public DealTypeRepository(DbContextOptions<MyContext> dbContextOptions)
        : base(dbContextOptions)
    {

    }
}

public class GenericRepository<TEntity> where TEntity : class
{
    private readonly DbContextOptions<MyContext> _dbContextOptions;

    public GenericRepository(DbContextOptions<MyContext> dbContextOptions)
    {
        _dbContextOptions = dbContextOptions;
    }

    public async Task<TEntity> Get(Expression<Func<TEntity, bool>> predicate, string code)
    {
        try
        {
            using (var db = new MyContext(_dbContextOptions))
            {
                using (var tr = db.Database.BeginTransaction(
                    IsolationLevel.ReadUncommitted))
                {
                    var entity = await db.Set<TEntity>().AsNoTracking()
                        .FirstAsync(predicate);

                    tr.Commit();

                    return entity;
                }
            }
        }
        catch (Exception e)
        {
            throw new Exception("Error on getting entity by code: {code}");
        }
    }
}

能否请您指导我如何检索CacheKeys类的必需属性以编写通用方法？我想可以很容易地通过反射来完成。

更新：我不确定是否要尝试一种通用方法，因为每个实体都有其自身名称的Id属性（例如，对于DealType为IdDealType，对于货币为IdCurrency）

Answer 1

开始之前：此解决方案假定您所有实体都遵循示例代码中显示的命名约定。

首先，最好有一个专用于此服务的存储库，在该存储库中可以按任何实体类型进行查询。在那里，您将使用约定来获取那些属性名称，并且可以使用EF.Property来查询它们。由于您的所有查询似乎都在“代码”列中，因此我们还可以简化该存储库方法中的参数。

public class ParamRepository : IParamRepository
{
    private readonly DbContextOptions<MyContext> _dbContextOptions;

    public ParamRepository(DbContextOptions<MyContext> dbContextOptions)
    {
        _dbContextOptions = dbContextOptions;
    }

    public async Task<(int id, string name)> GetParamsByCode<TEntity>(string code) where TEntity : class
    {
        string entityName = typeof(TEntity).Name;
        string idProp = $"Id{entityName}";
        string nameProp = $"{entityName}Name";
        try
        {
            using (var db = new MyContext(_dbContextOptions))
            {
              var entity = await db.Set<TEntity>().AsNoTracking()
                        .Where(p => EF.Property<string>(p, "Code") == code)
                        .Select(p => new { Id = EF.Property<int>(p, idProp), Name = EF.Property<string>(p, nameProp)})
                        .FirstAsync();

              return (id: entity.Id, name: entity.Name);
            }
        }
        catch (Exception e)
        {
            throw new Exception("Error on getting entity by code: {code}");
        }
    }
}

您还需要重构要根据约定创建的缓存键：

public static class CacheKeys
{
    public static string GetIdKey<TEntity>() => $"_Id{typeof(TEntity).Name}";
    public static string GetNameKey<TEntity>() => $"_{typeof(TEntity).Name}Name";
}

然后，在GetParamsService上变得很容易：

public class GetParamsService
{
    private readonly IMemoryCache _cache;
    private readonly MemoryCacheEntryOptions _cacheOptions;
    private readonly IParamRepository _paramRepository;

    public GetParamsService(IMemoryCache memoryCache,
        IParamRepository paramRepository)
    {
        _cache = memoryCache;
        _cacheOptions = new MemoryCacheEntryOptions()
            .SetSlidingExpiration(TimeSpan.FromHours(2));

        _paramRepository = paramRepository;
    }

    public async Task<(int id, string name)> GetParams<TEntity>(string code) where TEntity : class
    {
        string cacheIdKey = CacheKeys.GetIdKey<TEntity>();
        string cacheNameKey = CacheKeys.GetNameKey<TEntity>();
        if (!_cache.TryGetValue(cacheIdKey, out int cacheId)
            | !_cache.TryGetValue(cacheNameKey, out string cacheName))
        {
            var param = await _paramRepository.GetParamsByCode<TEntity>(code);

            cacheId = param.id;
            cacheName = param.name;

            _cache.Set(cacheIdKey, cacheId, _cacheOptions);
            _cache.Set(cacheNameKey, cacheName, _cacheOptions);
        }

        return (cacheId, cacheName);
    }
}

获取类的所需属性

1 个答案: