c# - 在构造函数中使用 Mapper.Initialize

Question

我正在使用 AutoMapper 将我的 POCO 映射到 DTO。对于单元可测试性，我将 IMapping 引擎传递到我的构造函数中，并在构造函数为 null 的情况下使用 Mapper.Initialize。

public class PeopleEfProvider : IPeopleDbContext
{
    public IMappingEngine MappingEngine { get; set; }
    public DatabaseHelpersRepo DatabaseHelpersRepo { get; set; }
    public PeopleDataContext DataContext { get; set; }
    public PeopleEfProvider(PeopleDataContext dataContext = null, IMappingEngine mappingEngine = null)
    {
        DataContext = dataContext ?? new PeopleDataContext();
        // if mappingEngine is coming from Unit Test or from another Client then use it.
        if (mappingEngine == null)
        {               
            Mapper.Initialize(mapperConfiguration =>
            {
                mapperConfiguration.AddProfile(new PeopleEfEntityProfile());
            });
            Mapper.AssertConfigurationIsValid();
            MappingEngine = Mapper.Engine;
        }
        else
        {
            MappingEngine = mappingEngine;
        }
        DatabaseHelpersRepo = new DatabaseHelpersRepo(DataContext, MappingEngine);
    }
}

以这种方式使用 AutoMapper 有什么缺点吗？我运行了 1000 多个循环的集成测试，没有发现任何问题，另一方面，当我把它放到网上时，我不能说它是否可行。

AutoMapper 会尝试在下一个对象创建时从头开始构建所有映射，还是它足够聪明，不会再次映射相同的对象？

Answer 1

Mapper.Initialize 只应在每个 AppDomain 中调用一次，如果您不在应用程序启动时调用它(App_Start 等)，您将遇到一些奇怪的线程问题。

你也可以创建一个惰性初始化器来完成同样的事情:

public class PeopleEfProvider : IPeopleDbContext
{
    private static Lazy<IMappingEngine> MappingEngineInit = new Lazy<IMappingEngine>(() => {
        Mapper.Initialize(mapperConfiguration =>
        {
            mapperConfiguration.AddProfile(new PeopleEfEntityProfile());
        });
        Mapper.AssertConfigurationIsValid();
        return Mapper.Engine;
    });
    public IMappingEngine MappingEngine { get; set; }
    public DatabaseHelpersRepo DatabaseHelpersRepo { get; set; }
    public PeopleDataContext DataContext { get; set; }
    public PeopleEfProvider(PeopleDataContext dataContext = null, IMappingEngine mappingEngine = null)
    {
        DataContext = dataContext ?? new PeopleDataContext();
        MappingEngine = mappingEngine ?? MappingEngineInit.Value;
        DatabaseHelpersRepo = new DatabaseHelpersRepo(DataContext, MappingEngine);
    }
}