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A comprehensive guide on using `AutoMapper` in C# to map properties from one object to another, especially when dealing with lists.
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How to Use AutoMapper for Mapping a List Property in C#

When working with data transfer objects (DTOs) in C# , situations often arise where you need to map one object’s properties to another. Specifically, if you have a list of properties in one object that needs to be transformed into multiple objects in another, like the case of EngineTMP mapping to EngineModelDto. In this post, we'll walk you through how to achieve this mapping efficiently using AutoMapper.

The Problem at Hand

Let’s consider a scenario where you have the following classes:

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You want to map an instance of EngineTMP to a list of EngineModelDto objects. The EngineTMP class may contain multiple CarIds, and for each CarId, you want to create a separate EngineModelDto object.

Manual Mapping Approach

Before diving into AutoMapper, you can accomplish this mapping manually, which is straightforward for such a simple scenario. Here’s how you can do it:

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This code snippet utilizes LINQ's Select method to iterate over the CarIds list and create new instances of EngineModelDto for each CarId.

Using AutoMapper for Mapping

If you prefer to use AutoMapper—a popular library that facilitates object-to-object mapping in C# —you can set it up for this scenario efficiently.

Configuring AutoMapper

To get started with AutoMapper, you need to create a mapping configuration. Here's how to configure the mapping from EngineTMP to IEnumerable<EngineModelDto>:

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This configuration tells AutoMapper how to convert an EngineTMP object by iterating over the CarIds and creating a new EngineModelDto for each ID.

Performing the Mapping

Once you have your mapping configuration in place, you can easily map an EngineTMP object to a list of EngineModelDto objects as follows:

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This single line simplifies your code and utilizes the power of AutoMapper to handle the repetitive mapping logic.

Conclusion

In summary, whether you choose to map manually or use AutoMapper, both methods will enable you to efficiently transform your data between object types in C# . For clean, maintainable code, particularly in larger applications, leveraging libraries like AutoMapper can significantly reduce boilerplate and improve readability.

By understanding these mapping techniques, you can improve your data handling capabilities in C# . Happy coding!