ABP框架实现通用CRUD领域服务时IRepository为空报错如何解决

错误原因 #

你抛出的System.ArgumentNullException: Value cannot be null. (Parameter 'source')错误，本质是_genericRepository字段为空，导致调用.Where()的时候触发空参数异常。
你没有给泛型基类GenericManager<T>编写构造函数实现依赖注入，ABP框架没法自动给你注入对应的仓储实例。

修复步骤 #

1. 给泛型基类补充构造函数注入仓储 #

修改GenericManager<T>的代码，添加带IRepository<T, int>参数的构造函数，让ABP的DI系统可以自动注入对应实体的仓储：

public class GenericManager<T>  : DomainService where T : class, IEntity<int>
{
    public readonly IRepository<T, int> _genericRepository;

    // 补充构造函数，实现仓储注入
    public GenericManager(IRepository<T, int> genericRepository)
    {
        _genericRepository = genericRepository;
    }

    public async Task<T> GetAsync(int id) => await AsyncExecuter.FirstOrDefaultAsync(_genericRepository.Where(m => m.Id == id));
    public async Task AddAsync(T entity) => await _genericRepository.InsertAsync(entity);
    public async Task AddManyAsync(IEnumerable<T> entities) => await _genericRepository.InsertManyAsync(entities);
    public async Task UpdateAsync(T entity) => await _genericRepository.UpdateAsync(entity);
    public async Task UpdateManyAsync(IEnumerable<T> entities) => await _genericRepository.UpdateManyAsync(entities);
    public async Task DeleteAsync(T entity) => await _genericRepository.DeleteAsync(entity);
}

2. 子类继承时调用基类构造函数 #

修改ClientManager，补充构造函数，把仓储传递给父类：

public class ClientManager : GenericManager<Client>
{
    // 子类构造函数接收仓储，传递给基类
    public ClientManager(IRepository<Client, int> repository) : base(repository)
    {
    }

    public async Task<Client> GetClientByNameAsync(string userName) => await AsyncExecuter.FirstOrDefaultAsync(_genericRepository.Where(m => m.UserName == userName));
    public async Task<Client> FindClientWithVKID(string vkid) => await AsyncExecuter.FirstOrDefaultAsync(_genericRepository.Where(m => m.VkId == vkid));
}

3. 可选优化（简化代码） #

ABP的仓储本身已经封装了GetAsync、InsertAsync等基础CRUD方法，你不需要自己用AsyncExecuter封装，直接调用仓储自带的方法即可，代码可以简化为：

public class GenericManager<T>  : DomainService where T : class, IEntity<int>
{
    public readonly IRepository<T, int> _genericRepository;

    public GenericManager(IRepository<T, int> genericRepository)
    {
        _genericRepository = genericRepository;
    }

    // 直接调用仓储原生方法即可
    public async Task<T> GetAsync(int id) => await _genericRepository.GetAsync(id);
    public async Task<T> AddAsync(T entity) => await _genericRepository.InsertAsync(entity);
    public async Task AddManyAsync(IEnumerable<T> entities) => await _genericRepository.InsertManyAsync(entities);
    public async Task<T> UpdateAsync(T entity) => await _genericRepository.UpdateAsync(entity);
    public async Task UpdateManyAsync(IEnumerable<T> entities) => await _genericRepository.UpdateManyAsync(entities);
    public async Task DeleteAsync(T entity) => await _genericRepository.DeleteAsync(entity);
}

额外注意点 #

如果你的Client实体没有默认注册仓储，可以在你的模块类的ConfigureServices方法里开启自动注册所有实体的默认仓储：

Configure<AbpEfCoreOptions>(options =>
{
    options.AddDefaultRepositories(includeAllEntities: true);
});

内容的提问来源于stack exchange，提问作者Jiggly Dezar