How can i add select columns in specification pattern

Question

How can i add select columns in specification pattern

AHSAN ALI 101

i followed this medium article

https://medium.com/@rudyzio92/net-core-using-the-specification-pattern-alongside-a-generic-repository-318cd4eea4aa

how can i add select like this in my specification class UsersWithRecipesAndIngredientsSpecification

   Select(o => new specialisation_sub { Id = o.Id, name = o.name })

Bruce (SqlWork.com) 78,401 Reputation points Volunteer Moderator

2023-11-26T21:36:00.06+00:00

as the specification is always based on an entity (DbSet), you would need to define a base entity that just contains the columns you want. you could implement a post query mapping api to map the query entry to a new entity.
Farid Uddin Kiron MSFT 456 Reputation points Microsoft External Staff

2023-11-27T03:15:59.9133333+00:00

Hi have you tired the solution provided? Did you able to resolve your issue? If you still have any further concern on this feel free to share.
AHSAN ALI 101 Reputation points

2023-11-27T15:06:08.7966667+00:00

@Farid Uddin Kiron MSFT no . Can you write sample code for me
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Farid Uddin Kiron MSFT 456 Reputation points Microsoft External Staff

2023-11-29T00:47:59.6233333+00:00

Hi @AHSAN ALI, I am not sure, if it is your solution or the problem you are having with? What exactly you are trying to achieve?
AHSAN ALI 101 Reputation points

2023-11-29T09:34:26.25+00:00

@Farid Uddin Kiron MSFT i am following medium artical for specification

Pattern it's working .

Now I want to add projection . I have user table with 15 columns

I want to get only 5 columns. Using specification pattern

But I am confused how can I get this .
Farid Uddin Kiron MSFT 456 Reputation points Microsoft External Staff

2023-12-05T09:31:00.3766667+00:00

Well, thanks for your response, while defining SpecificationEvaluator are you getting any error? How many column are you getting now?

AHSAN ALI 101

@Farid Uddin Kiron MSFT

thanks for your response

this is my evaluator class.

its return all 15 columns but i want to get only 5

    public class SpecificationEvaluator<TEntity> where TEntity :class
    {
        public static IQueryable<TEntity> GetQuery(IQueryable<TEntity> inputQuery, ISpecification<TEntity> specification)
        {
            var query = inputQuery;

            // modify the IQueryable using the specification's criteria expression
            if (specification.Criteria != null)
            {
                query = query.Where(specification.Criteria);
            }

            // Includes all expression-based includes
            query = specification.Includes.Aggregate(query,
                                    (current, include) => current.Include(include));

            // Include any string-based include statements
            query = specification.IncludeStrings.Aggregate(query,
                                    (current, include) => current.Include(include));

            // Apply ordering if expressions are set
            if (specification.OrderBy != null)
            {
                query = query.OrderBy(specification.OrderBy);
            }
             if (specification.OrderByDescending != null)
            {
                query = query.OrderByDescending(specification.OrderByDescending);
            }
            if (specification.OrderByDateDescending != null)
            {
                query = query.OrderByDescending(specification.OrderByDateDescending);
            }

            if (specification.GroupBy != null)
            {
                query = query.GroupBy(specification.GroupBy).SelectMany(x => x);
            }
         
         

            // Apply paging if enabled
            if (specification.IsPagingEnabled && specification.Take>0)
            {
                query = query.Skip(specification.Skip)
                             .Take(specification.Take);
            }
            if (specification.Take>0)
            {
                query = query.Take(specification.Take);
            }
            if (specification.AsNoTrackingEnabled)
            {
                query = query.AsNoTracking();
            }
            return query;
        }
    }

Bruce (SqlWork.com) 78,401 Reputation points Volunteer Moderator

2023-12-05T23:23:01.9666667+00:00

the .Select() is used for projection. any caller can apply projection on the query.

if you want to use in the specification generic, them you need to define a mapper that maps the Entity -> SubsetEntity. as this would be generic you could use reflection or a library like automapper.

https://automapper.org

2 answers

Your answer

Bruce (SqlWork.com) 78,401 Reputation points Volunteer Moderator

2023-11-26T21:36:00.06+00:00

as the specification is always based on an entity (DbSet), you would need to define a base entity that just contains the columns you want. you could implement a post query mapping api to map the query entry to a new entity.
Farid Uddin Kiron MSFT 456 Reputation points Microsoft External Staff

2023-11-27T03:15:59.9133333+00:00

Hi have you tired the solution provided? Did you able to resolve your issue? If you still have any further concern on this feel free to share.
AHSAN ALI 101 Reputation points

2023-11-27T15:06:08.7966667+00:00

@Farid Uddin Kiron MSFT no . Can you write sample code for me
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Farid Uddin Kiron MSFT 456 Reputation points Microsoft External Staff

2023-11-29T00:47:59.6233333+00:00

Hi @AHSAN ALI, I am not sure, if it is your solution or the problem you are having with? What exactly you are trying to achieve?
AHSAN ALI 101 Reputation points

2023-11-29T09:34:26.25+00:00

@Farid Uddin Kiron MSFT i am following medium artical for specification

Pattern it's working .

Now I want to add projection . I have user table with 15 columns

I want to get only 5 columns. Using specification pattern

But I am confused how can I get this .
Farid Uddin Kiron MSFT 456 Reputation points Microsoft External Staff

2023-12-05T09:31:00.3766667+00:00

Well, thanks for your response, while defining SpecificationEvaluator are you getting any error? How many column are you getting now?
AHSAN ALI 101 Reputation points

2023-12-05T20:56:08.2233333+00:00

@Farid Uddin Kiron MSFT

thanks for your response

this is my evaluator class.

its return all 15 columns but i want to get only 5

public class SpecificationEvaluator<TEntity> where TEntity :class { public static IQueryable<TEntity> GetQuery(IQueryable<TEntity> inputQuery, ISpecification<TEntity> specification) { var query = inputQuery; // modify the IQueryable using the specification's criteria expression if (specification.Criteria != null) { query = query.Where(specification.Criteria); } // Includes all expression-based includes query = specification.Includes.Aggregate(query, (current, include) => current.Include(include)); // Include any string-based include statements query = specification.IncludeStrings.Aggregate(query, (current, include) => current.Include(include)); // Apply ordering if expressions are set if (specification.OrderBy != null) { query = query.OrderBy(specification.OrderBy); } if (specification.OrderByDescending != null) { query = query.OrderByDescending(specification.OrderByDescending); } if (specification.OrderByDateDescending != null) { query = query.OrderByDescending(specification.OrderByDateDescending); } if (specification.GroupBy != null) { query = query.GroupBy(specification.GroupBy).SelectMany(x => x); } // Apply paging if enabled if (specification.IsPagingEnabled && specification.Take>0) { query = query.Skip(specification.Skip) .Take(specification.Take); } if (specification.Take>0) { query = query.Take(specification.Take); } if (specification.AsNoTrackingEnabled) { query = query.AsNoTracking(); } return query; } }
Bruce (SqlWork.com) 78,401 Reputation points Volunteer Moderator

2023-12-05T23:23:01.9666667+00:00

the .Select() is used for projection. any caller can apply projection on the query.

if you want to use in the specification generic, them you need to define a mapper that maps the Entity -> SubsetEntity. as this would be generic you could use reflection or a library like automapper.

https://automapper.org

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Answer 2

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How can i add select columns in specification pattern

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