Automapper的用途是什么? [英] What's Automapper for?

问题描述

Automapper 的用途是什么?

它对我的域和控制器层(asp.net mvc)有什么帮助?

How will it help me with my domain and controller layers (asp.net mvc)?

推荐答案

也许一个示例在这里会有所帮助...

Maybe an example will help here...

假设您有一个很好的标准化数据库架构，如下所示:

Let's say you have a nicely-normalized database schema like this:

Orders       (OrderID, CustomerID, OrderDate)  
Customers    (CustomerID, Name)  
OrderDetails (OrderDetID, OrderID, ProductID, Qty)  
Products     (ProductID, ProductName, UnitPrice)  

假设您使用的是一个不错的O/R映射器，它将使您拥有井井有条的域模型:

And let's say you're using a nice O/R mapper that hands you back a well-organized domain model:

OrderDetail
+--ID
+--Order
|--+--Date
|--+--Customer
|-----+--ID
|-----+--Name
+--Product
|--+--ID
|--+--Name
|--+--UnitPrice
+--Qty

现在，您需要显示上个月订购的所有商品.您希望将其绑定到平面网格，因此您有义务编写一个平面类进行绑定:

Now you're given a requirement to display everything that's been ordered in the last month. You want to bind this to a flat grid, so you dutifully write a flat class to bind:

public class OrderDetailDto
{
    public int ID { get; set; }
    public DateTime OrderDate { get; set; }
    public int OrderCustomerID { get; set; }
    public string OrderCustomerName { get; set; }
    public int ProductID { get; set; }
    public string ProductName { get; set; }
    public Decimal ProductUnitPrice { get; set; }
    public int Qty { get; set; }

    public Decimal TotalPrice
    {
        get { return ProductUnitPrice * Qty; }
    }
}

到目前为止，这还算很轻松，但是现在呢?我们如何将一堆OrderDetail变成一堆OrderDetailDto进行数据绑定?

That was pretty painless so far, but what now? How do we turn a bunch of OrderDetails into a bunch of OrderDetailDtos for data binding?

您可能会在OrderDto上放置一个构造器，该构造器需要一个OrderDetail，并编写大量的映射代码.或者您可能在某个地方有一个静态转换类.或者，您可以使用AutoMapper来代替它:

You might put a constructor on OrderDto that takes an OrderDetail, and write a big mess of mapping code. Or you might have a static conversion class somewhere. Or, you could use AutoMapper, and write this instead:

Mapper.CreateMap<OrderDetail, OrderDetailDto>();
OrderDetailDto[] items =
    Mapper.Map<OrderDetail[], OrderDetailDto[]>(orderDetails);
GridView1.DataSource = items;

在那里.我们已经采用了原本会令人厌恶的无意义的映射代码，然后将其简化为三行(对于实际映射，实际上只有两行).

There. We've just taken what would otherwise have been a disgusting mess of pointless mapping code and reduced it into three lines (really just two for the actual mapping).

这有助于解释目的吗?

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