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Define DTO(Data Transfer Object). How to use Data Transfer Objects in ASP.NET Core 3.1

Updated: Mar 18, 2023



Data Transfer Object (DTO)

a Data Transfer Object (DTO) is a pattern used to transfer data between software components, particularly between the application layer and the presentation layer. A DTO is a plain C# or Java object that contains properties for storing data. DTOs are typically used to encapsulate data that needs to be transferred between different layers of an application or between different applications, such as from a web API to a client application.


In ASP.NET Core 3.1, Data Transfer Objects (DTOs) are commonly used to transfer data between the API controller and the client application. The use of DTOs helps to decouple the data model from the API response and provides better control over the data returned to the client.


OOP environments rely on a system of "calls." Each one is a bit like a data lookup, and they require both time and processing speed. If you’re not careful, calls can also expose sensitive data you'd like to keep hidden, such as:

  • Employee addresses

  • Account numbers

  • Social Security numbers

  • Business logins

As one programmer explains, you might require an employee's name and photo to enter your company. You need to provide that data for a match, but you don't need to give other information about the employee that you have within your database. A DTO can transfer only the information required.

Data Transfer Objects have only public fields, and these fields may have one of a limited set of types. This limits the risk of unnecessary coupling between modules, allows DTOs to be easily serialized (even though they are not java.io.Serializable), and makes DTOs easy to transform using the OSGi Converter. DTOs are therefore excellent candidates for service API parameters and return values, they can be used remotely, or outside of Java, and can be represented using JSON, YAML or any format of your choice.



Architecture



How to put a DTO to use

A DTO should just contain data, not business logic. It's a simple, small thing that should do one task only.


A good DTO will:

  • Minimize boilerplate. You'll write each one fresh.

  • Be easy to create. DTOs shouldn't be so complicated that you struggle to write them. (Code like this is easy to break.)

  • Be readable. Anyone should be able to parse your code.

How to use Data Transfer Objects in ASP.NET Core 3.1

Here are the steps to use Data Transfer Objects in ASP.NET Core 3.1:


Step 1: Create a Data Transfer Object (DTO) class

Create a new class with the properties that you want to transfer between the API controller and the client application.

public class ProductDTO
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}


Step 2: Map the DTO to the Domain Model

Create a mapping function that maps the DTO to the Domain Model. This mapping function helps to map the properties of the DTO to the Domain Model properties.

public static ProductDTO ToDTO(this Product product)
{
    return new ProductDTO
    {
        Id = product.Id,
        Name = product.Name,
        Price = product.Price
    };
}


Step 3: Use the DTO in the API Controller

In the API Controller, use the DTO to transfer data between the controller and the client application.

[HttpGet]
public async Task<ActionResult<IEnumerable<ProductDTO>>> GetProducts()
{
    var products = await _repository.GetProductsAsync();
    return Ok(products.Select(product => product.ToDTO()));
}

In the above example, the GetProducts() method returns a list of products as a collection of ProductDTOs by calling the ToDTO() extension method on each product.


Step 4: Use the DTO in the Client Application

In the client application, use the DTO to deserialize the response data returned by the API controller.

public async Task<IEnumerable<ProductDTO>> GetProductsAsync()
{
    var response = await httpClient.GetAsync("api/products");
    response.EnsureSuccessStatusCode();
    var content = await response.Content.ReadAsStringAsync();
    return JsonSerializer.Deserialize<IEnumerable<ProductDTO>>(content, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });
}

In the above example, the GetProductsAsync() method sends a GET request to the API endpoint and deserializes the response data to a collection of ProductDTOs using the System.Text.Json.JsonSerializer class.

Why use Data Transfer Objects (DTOs)?

Data Transfer Objects (DTOs) are used in ASP.NET Core to transfer data between the API controller and the client application. DTOs help to decouple the data model from the API response and provide better control over the data returned to the client.


Here are some of the main reasons to use DTOs in ASP.NET Core:

  1. Decoupling of data models: DTOs help to decouple the data model from the API response. This separation enables developers to make changes to the data model without affecting the API response. It also makes it easier to maintain the code by separating concerns.

  2. Improved performance: By using DTOs, you can reduce the amount of data transferred between the client and server. DTOs allow you to transfer only the required data, which helps to improve the performance of the application.

  3. Better control over the data returned to the client: By using DTOs, you can control the data returned to the client more effectively. DTOs can be used to exclude sensitive data or limit the amount of data returned to the client.

  4. Easy to maintain: By using DTOs, you can create a clear separation of concerns in your code. This makes it easier to maintain the code over time, as changes to the data model can be made without affecting the API response.

Challenges for Data Transfer Object in ASP.NET Core

While Data Transfer Objects (DTOs) provide a lot of benefits in ASP.NET Core, there are also some challenges associated with using them. Here are some of the common challenges that developers may face when working with DTOs:

  1. Increased complexity: As the application grows, the number of DTOs required can increase significantly. This can result in an increase in the complexity of the application, making it harder to maintain and understand.

  2. Additional code overhead: Creating DTOs requires additional code overhead. Each DTO must be defined and mapped to the corresponding domain model. This can add to the development time and effort required.

  3. Versioning issues: Versioning can be challenging when using DTOs. If changes are made to the domain model, the corresponding DTOs must be updated as well. This can cause versioning issues when multiple clients are accessing the API, especially if they are using different versions of the API.

  4. Data validation issues: DTOs may not always provide complete data validation. Data validation must be performed on both the server-side and client-side, and any discrepancies between the two can result in data integrity issues.

  5. Performance issues: Using DTOs can result in additional performance overhead. This is especially true if there are a large number of DTOs being used or if the DTOs are not properly optimized.


Conclusion:

Using Data Transfer Objects (DTOs) in ASP.NET Core 3.1 is a simple and effective way to transfer data between the API controller and the client application. DTOs help to decouple the data model from the API response and provide better control over the data returned to the client. By following the steps outlined in this article, you can easily implement DTOs in your ASP.NET Core 3.1 application.

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