How to manage DTO Implementaion for Rest-Api in .NET CORE? Alternatives? - rest

Question

I have a quite big query in my WebApi which filters data from different models to send them in a DTO Object to FrontEnd(Angular).
I think DTO could be the right approach because it isn't neccessary for the frontend to get all parameters from all models.
My problem consists in from mapping the DTO Object back to my WebApi Models.
I tried Automapper from NugetPackages but it didn't work. I also heard that AutoMapper isn't the right choice when projects are getting bigger and bigger.
Below is the Code for my DTO object, query and models:
public class ApplicationSettingsDto
{
public string KeyName { get; set; }
public string Wert { get; set; }
public string DefaultValue { get; set; }
public string Description { get; set; }
}
Models:
public partial class ApplicationSettings
{
public string KeyName { get; set; }
public string Wert { get; set; }
public int Typ { get; set; }
public string DisplayOrder { get; set; }
}
public partial class ApplicationSettingsDefaults
{
public Guid Id { get; set; }
public string KeyName { get; set; }
public string Value { get; set; }
public int ProduktOption { get; set; }
}
public partial class Text
{
public string KeyName { get; set; }
public string Sprache { get; set; }
public string Text1 { get; set; }
public DateTime LetzteAenderung { get; set; }
}
Query:
public IQueryable Description()
{
int produktOption = GetProduktOption();
var query = from appl in _repositoryContext.ApplicationSettings
from text in _repositoryContext.Text
from defaults in _repositoryContext.ApplicationSettingsDefaults
//filter DefaultValues
where appl.KeyName.Equals(defaults.KeyName) &&
(defaults.ProduktOption.Equals(produktOption) || defaults.ProduktOption.Equals(65535))
//Filter TextValues
where EF.Functions.Like(text.KeyName, "%" + appl.KeyName) ||
EF.Functions.Like(text.KeyName, "%" + appl.KeyName + "$Descr")
where EF.Functions.Like(text.Sprache, "de-DE")
select new ApplicationSettingsDto()
{
KeyName = appl.KeyName,
Wert = appl.Wert,
DefaultValue = defaults.Value,
Description = text.Text1
}
into output orderby output.KeyName select output;
return query;
}
So this question is not about an detailed implementation, it's only about recommendations for implementing DTO because mapping can be a pain in the *ss, like in my example.
I'm open to new ideas or patterns I don't know yet to try to manage problems like this.
Thanks in Advance ;)

Answer 1

This question is likely to be closed as you have working code, but my recommendation, after years of having tried AutoMapper, reflection based mappings, and hand-written mappings, that you should just stick with what is simplest and works.
You typically have to write the mapping logic for your DTOs once. The code you would write is legible and straightforward. When you move that to AutoMapper, you now end up having an often unrelated and less legible piece of code for something very, very simple.
In the event that you need the mapping logic in another function, extract it to a separate method. In the event that you need it in a separate class, promote that mapping function to a static method on your DTO.
Most of my mapping code looks like:
// Some controller code
da.GetStudents().Select(Map); // Map is the function below
In the controller, the following method is defined:
public StudentDto Map(Student student)
{
if (student == null) return null;
return new StudentDto
{
FirstName = student.FirstName,
...
};
}
Hope that helps.