【C#】Lazy<T> 类 官方说明: https://docs.microsoft.com/zh-cn/dotnet/api/system.lazy-1?view=net-5.0 实例:https://github.com/abpframework/abp/blob/dev/framework/src/Volo.Abp.EntityFrameworkCore/Volo/Abp/Domain/Repositories/EntityFrameworkCore/EfCoreRepository.cs