4

I am trying to utilize the Ardalis.Specification library to apply the specification pattern in my asp.net 6 project.

After installing the library, I created the following specification

public class ProductByIdsSpec : Specification<Product, ProductMenuItem>
{
    public ClientRecordByIdsSpec(IEnumerable<int> ids)
    {
        if (ids == null || !ids.Any())
        {
            return;
        }

        Query.Where(x => ids.Contains(x.Id));


        // some how I need to map Product to ProductMenuItem so only the needed columns are pulled from the database.
    }

}

Instead of pulling every value in Product from the database, I want to only pull the needed data by projecting the data to ProductMenuItem. The above specification is returning the following error

SelectorNotFoundException Ardalis.Specification.SelectorNotFoundException: The specification must have Selector defined

How can I define the map between entity (i.e., Product) and and the result object (i.e., ProductMenuItem)?

I tried to add Select() definition but is giving me the same error

public class ProductByIdsSpec : Specification<Product, ProductMenuItem>
{
    public ClientRecordByIdsSpec(IEnumerable<int> ids)
    {
        if (ids == null || !ids.Any())
        {
            return;
        }

        Query.Where(x => ids.Contains(x.Id));


        Query.Select(x => new ProductMenuItem() { Name = x.Name, x.Id = x.Id });
    }

}
Jay
  • 1,168
  • 13
  • 41

1 Answers1

0
public class ProductByIdsSpec : Specification<Product, ProductMenuItem>
{
    public ClientRecordByIdsSpec(IEnumerable<int> ids)
    {
        ...
    }

    public override Expression<Func<Product, ProductMenuItem>> Selector { get; }
        = (product) => new ProductMenuItem();
}

You can override the Selector property in your Specification class and implement your projection there

https://github.com/ardalis/Specification/blob/main/Specification/src/Ardalis.Specification/Specification.cs#L29

Victor Hilliard
  • 1