具有通用扩展方法的 AutoMapper 映射

Question

我想用通用扩展方法映射我的对象。

public class Customer    
{    
    public string FirstName { get; set; }    
    public string LastName { get; set; }    
    public string Email { get; set; }    
    public Address HomeAddress { get; set; }    
    public string GetFullName()    
    {  
        return string.Format(“{0} {1}”, FirstName, LastName);
    }    
}

这是视图模型

public class CustomerListViewModel    
{    
    public string FullName { get; set; }
    public string Email { get; set; }    
    public string HomeAddressCountry { get; set; }    
}

所以我正在创建地图，Mapper.CreateMap<Customer, CustomerListViewModel>();

我想创建一个扩展方法

public static class MapperHelper
{
    public static CustomerListViewModel ToViewModel(this Customer cust)
    {
        return AutoMapper.Mapper.Map<Customer, CustomerListViewModel>(cust);
    }
}

但我想让这个助手通用化：

public static class MapperHelper<TSource, TDest>
{
    public static TDest ToViewModel(this TSource cust)
    {
        return AutoMapper.Mapper.Map<TSource, TDest>(cust);
    }
}

给出错误：扩展方法只能在非泛型、非嵌套静态中声明class

如果我不能制作通用的，我应该为所有映射创建助手 class。有什么办法解决吗？

Answer 1

你就不能这样做吗？:

public static class MapperHelper
{
    public static TDest ToViewModel<TSource, TDest>(this TSource cust)
    {
       return AutoMapper.Mapper.Map<TSource, TDest>(cust);
    }
}

Answer 2

您不能在泛型中定义扩展方法 class 因为您无法在调用它时指定类型参数！

public static class MapperHelper<TSource, TTarget>
{
  public static TTarget ToViewModel(this TSource source)
  {
    ...
  }
}

...

// this is no problem if we invoke our method like a
// static method:-
var viewModel = MapperHelper<MyModel, MyViewModel>.ToViewModel(model);

// but if we use the extension method syntax then how
// does the compiler know what TSource and TTarget are?:-
var viewModel = model.ToViewModel();

您必须改为方法通用：-

public static class MapperHelper
{
  public static TTarget ToViewModel<TSource, TTarget>(this TSource source)
  {
    ...
  }
}

...

var viewModel = model.ToViewModel<MyModel, MyViewModel>();

Answer 3

比这些解决方案更好的是使用非通用 Map 方法：

public static class MapperHelper
{
    public static TDest MapTo<TDest>(this object src)
    {
        return (TDest)AutoMapper.Mapper.Map(src, src.GetType(), typeof(TDest));
    }
}

在您的代码中：

var model = customter.MapTo<CustomerViewModel>();

现在您的泛型方法中不需要多余的 Source 类型。

具有通用扩展方法的 AutoMapper 映射

AutoMapper mapping with generic extension methods

c#

generics

automapper