what is more suitable looping or db calls

• Avoid multiple DB calls if possible; prefer a single optimized query.
• Use projections and grouping to reduce unnecessary data fetching and looping.
• Consider using Include and ThenInclude to automatically load related entities without having to explicitly join them  (Look at the Example 1).
• If the result set is too large, consider using pagination or filtering techniques to reduce the amount of data processed at once (Look at the Example 2).
• Move the logic to stored procedures for heavy and complex queries if performance is an issue.

Example 1:

var candidate = context.Candidates
                       .Include(c => c.Ad)
                       .Include(c => c.B)
                       .Include(c => c.Skill)
                       .Include(c => c.Exp)
                       .FirstOrDefault(c => c.Id == id);

Example 2 :

var data = context.GetModel()
                  .Where(x => x.Id == id)
                  .Skip(pageSize * pageIndex)
                  .Take(pageSize)
                  .ToList();

Hello Umair,

Please use Include to do eager loading and select only specific fields which you need

var data = context.GetModel()
    .Include(a => a.Ad) 
    .Include(a => a.B) 
    .Include(a => a.C) 
    .Include(a => a.D) 
    .Where(a => a.Id == id) // Apply where condition if you have any filter or you can remove
    .Select(a => new
    {
        ac = a.Ad.Select(ad => new { ad.SomeField1, ad.SomeField2 }), // Replace with actual properties and use fetch only specific fields you need
        ce = a.B.Select(b => new { b.SomeField1, b.SomeField2 }),
        skill = a.C.Select(c => new { c.SomeField1, c.SomeField2 }),
        exp = a.D.Select(d => new { d.SomeField1, d.SomeField2 })
    }).ToList();

In scenarios where you are joining multiple tables and retrieving a large dataset, as illustrated in your LINQ query, it is generally more efficient to minimize database calls. Instead of executing multiple database calls, which can lead to performance bottlenecks, consider leveraging the power of LINQ to project the necessary data in a single query.

If you find yourself needing to loop through the results to access specific properties, you can utilize LINQ's SelectMany or GroupBy methods to flatten the data structure, reducing the need for nested loops.

var result = data.SelectMany(x => new[] { x.ce, x.skill, x.exp }).ToList();

This approach allows you to access the required data without excessive looping. However, if the dataset is too large and performance is a concern, consider implementing pagination or filtering to limit the data returned from the database.

Hi Umair,

You can use Navigation property.

var data = context.Candidates
                 .Include(c => c.Applications)
                 .Include(c => c.Skills)
                 .Include(c => c.Experience)
                 .Where(c => c.Id == id)
                 .Select(c => new
                 {
                     Candidate = c,
                     Applications = c.Applications,
                     Skills = c.Skills,
                     Experience = c.Experience
                 })
                 .ToList();

Project into a DTO

public class CandidateDto
{
    public Candidate Candidate { get; set; }
    public IEnumerable<Application> Applications { get; set; }
    public IEnumerable<Skill> Skills { get; set; }
    public IEnumerable<Experience> Experience { get; set; }
}

// In your query
var data = context.Candidates
                 .Include(c => c.Applications)
                 .Include(c => c.Skills)
                 .Include(c => c.Experience)
                 .Where(c => c.Id == id)
                 .Select(c => new CandidateDto
                 {
                     Candidate = c,
                     Applications = c.Applications,
                     Skills = c.Skills,
                     Experience = c.Experience
                 })
                 .ToList();

The best approach depends on your specific use case, including how often you need the related data, the size of the data sets, and performance considerations. Using navigation properties and DTOs tends to be cleaner and often performs well.

i am really thankful to all of you for sucha qucik response to my question.one more pain i wnt to give that i am sending this data to a view and my view is not ienumrable type.i declare these fields as iCollection in my candidate model and this model passed to view  and i use this code:

 var data = (from x in db.Candidates.Include("Academics").
                          Include("Certifications").
                          Include("Skills").
                          Include("Experiences")
                        where x.Id == id
                        select new
                        {
                            a = x.Skills,
                            b = x.Academics,
                            c = x.Experience,
                            d = x.Certifications,
                            e = x
                        }).ToList().Select(c => new Candidate
                        {

                            Academics = c.b,
                            Skills = c.a,
                            Experience = c.c,
                            Certifications = c.d,
                          profile=c.e

                        }).FirstOrDefault() ;

if i do not use second select statement in which there is a new Candidate{}, i can't get candidate table values which are stored in annonymous variable e i have debug this i got candidate table null . what i did in my candidate model i declare a field of candidate type and store candidate table values in it, then pass this whole var data to my view as this  variable is of type candidate now so i can pass it to my view by doing this i got whole my candidate table values and other related values.

i want to ask that declaring candidate type field in a candidate model is ok or not.is thisa good practice.

declaring a Candidate type field within the Candidate model itself is not a good practice. By having a Candidate property within the Candidate model, you're creating a circular dependency. This can lead to serialization issues, infinite loops, and difficulties in mapping data.

Better approach, Remove the self-referential composition and flatten the data into separate properties within the Candidate model.

public class Candidate
{
    public int Id { get; set; }
   
    public ICollection<Academic> Academics { get; set; }
    public ICollection<Skill> Skills { get; set; }
    public ICollection<Experience> Experiences { get; set; }
    public ICollection<Certification> Certifications { get; set; }
}

Create a separate view model that contains the required properties from the Candidate model and related entities.

public class CandidateViewModel
{
    public Candidate Candidate { get; set; }
    public ICollection<Academic> Academics { get; set; }
    public ICollection<Skill> Skills { get; set; }
    public ICollection<Experience> Experiences { get; set; }
    public ICollection<Certification> Certifications { get; set; }
}