Generic method to retrieve DbSet from DbContext and Using Include() method c#

Question

I made this function that retrieves all the data.

public static List<Volunteer> GetAllVolunteers()
{
    using (VolunteerPlacementSystemDBEntities1 db = new VolunteerPlacementSystemDBEntities1())
    {
        return db.Volunteers.**Include(v => v.roleForVolunteers).Include(v => v.VolunteerOffers)
                         .Include("VolunteerOffers.daysForAVolunteers")**.ToList();
    }
}

And I have this generic function that retrieves DBSet T.

public static List<T> GetDbSet<T>() where T : class
{
    using (VolunteerPlacementSystemDBEntities1 db = new VolunteerPlacementSystemDBEntities1())
    {
        return db.GetDbSet<T>().ToList();
    }
}

Can I make a generic function that will retrieve all the data that connect to one DBSet T?

Thanks in advance.

Does this answer your question? [Entity Framework - Include / Reference / Collection](https://stackoverflow.com/questions/18072243/entity-framework-include-reference-collection) — Etheraex, May 24 '22 at 10:57
You need to use Reflection for extract all your Property from T that can include. — Den, May 24 '22 at 11:35

Nayan · Answer 1 · 2022-05-25T09:45:57.720

1

Get DbSet for the T Entity Class Type from context as DbSet<T> or IQueryable<T>.

On this IQueryable<T> object can perform multiple operations like Where(), Include(), orderBy() etc with help of namespace System.Linq.

With Include() method, pass on required included properties.
For Parallel processing use TPL from System.Threading.Tasks

Try this:

public static List<T> GetDbSet<T>(string[] includeProperties) where T : class
{
    using (VolunteerPlacementSystemDBEntities1 db = new VolunteerPlacementSystemDBEntities1())
    {
        IQueryable<T> query = db.Set<T>();

        Parallel.ForEach(inlcudeProperties, includeProperty => {
           query.Include(includeProperty);
        });

        return query.ToList();
    }
}

edited May 25 '22 at 09:45

answered May 24 '22 at 11:31

Nayan

471
2
9

I'm grateful Can you maybe tell me how I also give a Include of two levels? i made this array for example: public static string[] include { get; set; } = { "roleForVolunteers", "VolunteerOffers", " VolunteerOffers.daysForAVolunteers " }; and this: VolunteerOffers.daysForAVolunteers gave me an error – N.A May 24 '22 at 11:50
have VolunteerOffers be virtual property in T class and exclude that item from list. So you can be able to access that daysForVolunteers from virtual property – Nayan May 24 '22 at 11:57
VolunteerOffers is virtual already – N.A May 24 '22 at 12:03
public static string[] include { get; set; } = [ "roleForVolunteers", "VolunteerOffers" ]; – Nayan May 24 '22 at 12:06
2

If you need this, you can try change string[] parameter with `IIncludableQueryable> includesFunc` and then `includesFunc(query)` – Den May 24 '22 at 12:11
1

thanks, but i don't understand on what the error – N.A May 24 '22 at 13:05
1

System.InvalidOperationException: 'The context cannot be used while the model is being created.... – N.A May 24 '22 at 13:09
1

Add MultipleActiveResultSets=true in connection string. – Nayan May 24 '22 at 13:12

Den · Answer 2 · 2022-05-24T13:39:15.500

Some month ago i try to do somthing like that, but i have tableName. I leave you some detail, that you can adapt

You extract form context all your table and select only the ClrType corrispond with your T type.

var selectedTable = contextDb.Model
            .GetEntityTypes()
            .Select(x => new TableSpecification // Custom class
            {
                TableName = x.GetTableName(),
                ClrType = x.ClrType,
                JoinTable = x.GetForeignKeys(),
                JoinTableProp = x.GetForeignKeyProperties(),
                NavigationProp = x.GetNavigations(),
                ColumnsTable = null
            })
           .Where(// where ClrType)
           .Distinct()
           .FirstOrDefault();

This is my custom class

using Microsoft.EntityFrameworkCore.Metadata;

using System;
using System.Collections.Generic;

namespace Seac.CRM.DbInfrastructure.Model.Context;

public class TableSpecification
{
    public string TableName { get; init; }
    public Type ClrType { get; init; }
    public IEnumerable<IForeignKey> JoinTable { get; init; }
    public IEnumerable<IProperty> JoinTableProp { get; init; }
    public IEnumerable<INavigation> NavigationProp { get; init; }
    public IEnumerable<IProperty> ColumnsTable { get; init; }
}

then you can extract all your reference property

var joinLookup = selectedTable.JoinTable.GetLookupForeignKey();

foreach (var lookup in joinLookup)
   queryable = queryable.Include(lookup.PrincipalEntityType.Name.Split(".").Last());

I wish that can help you.

*** EDIT

If you need a custom include of T you can use IIncludableQueryable<T, object>>

public static List<T> GetDbSet<T>(IIncludableQueryable<T, object>> include = null) where T : class
{
    using (VolunteerPlacementSystemDBEntities1 db = new VolunteerPlacementSystemDBEntities1())
    {
        IQueryable<T> query = db.Set<T>();

        if (includesFunc is not null)
            query = includesFunc(query);

        return query.ToList();
    }
}

score 0 · Accepted Answer · answered May 29 '22 at 21:10

Thanks to everyone who tried to help me. This is the solution that worked for me.

  public static List<T> GetDbSetWithIncludes<T>(string[] includes) where T : class
    {
        using (VolunteerPlacementSystemDBEntities1 db = new VolunteerPlacementSystemDBEntities1())
        {
            db.Configuration.LazyLoadingEnabled = false;
            return IncludeMultiple<T>(db.GetDbSet<T>(), includes).ToList();
        }
    }


 public static IQueryable<T> IncludeMultiple<T>(IQueryable<T> query, string[] includes)where T : class
        {
            if (includes != null)
            {
                query = includes.Aggregate(query, (current, include) =>
                current.Include(include));
            }
            return query;
        }

Generic method to retrieve DbSet from DbContext and Using Include() method c#

3 Answers3