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Reference to multiple rows entity-framework?

By : user2175316
Date : October 15 2020, 08:10 PM
I wish did fix the issue. If one row of a database table relates to several rows in another table of the same database, then we say that there is a one-to-many relation between those two tables.
For example: a table with Schools and a table with Students. Every School in the table of Schools has zero or more Students from the table of Students.
code :
class School
    public int Id {get; set;}          // will become the primary key
    public string Name {get; set;}
    ... // other properties

    // every School has zero or more Students (one-to-many)
    public virtual ICollection<Student> Students {get; set;}

class Student
    public int Id {get; set;}          // will become the primary key
    public string Name {get; set;}
    public DateTime BirthDate {get; set;}
    ... // other properties

    // every Student belongs to exactly one School, using foreign key:
    public int SchoolId {get; set;}
    public virtual School School {get; set;}
class SchoolContext : DbContext
    public DbSet<School> Schools {get; set;}
    public DbSet<Student> Students {get; set;}
var result = dbContext.Students.Join(dbContext.Schools, // join students and schools
    student => student.SchoolId,                        // from Student take the SchoolId,
    school => school.Id,                                // from School take the Id,
    (student, school) => new                            // when they match, make a new object
        StudentName = student.Name,
        SchoolName = school.Name,
var result = dbContext.Students.Select(student => new
     StudentName = student.Name,
     SchoolName = student.School.Name,
var schoolsWithTheirStudents = dbContext.Schools.Select(school => new
     Name = school.Name,
     StudentNames = school.Students.Select(student => student.Name).ToList(),

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How to return multiple rows with entity framework, and sequentially reading them on multiple threads

By : John Wong
Date : March 29 2020, 07:55 AM
it should still fix some issue You can easily buffer a few million objects in memory. Buffer the results of the T-SQL in a List and pass that list to your worker threads.

Multiple contexts with Entity Framework 6, reference entities across dbcontexts

By : Yatheen archie
Date : March 29 2020, 07:55 AM
this one helps. The easiest approach would be to link tables from one database to the other so that this is the database server which handles two physical databases as one virtual database.
Then, in EF, you have just one context with tables from both databases and querying/joins etc. works correctly.

How can I delete multiple rows with Entity Framework?

By : Donkey
Date : March 29 2020, 07:55 AM
this will help I have this code but it doesn't work :
code :
    MPortalContext db=new MPortalContext();
    foreach (var item in _ModulID)
        var validation = db.WebSite_PermissionDB.Where(x => x.UserID == _UserID && x.ModuleID == item).FirstOrDefault();
    return true;

Entity Framework - Code First - Allowing Multiple Entities to reference a single entity

By : tejas123
Date : March 29 2020, 07:55 AM
I wish this help you you need to add a ICollection Planets in your Mineral class :
code :
public class Mineral
    public Mineral()
        Planets = new HashSet<Planet>();

    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int ID { get; set; }
    public string Name { get; set; }
    public string Symbol { get; set; }
    public string Mineral_Desc { get; set; }
    public int rate { get; set; }
    public decimal ratio { get; set; }

    public virtual ICollection<Planet> Planets { get; set; }        
public class Planet
    public Planet()
        Minerals = new HashSet<Mineral>();

    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int ID { get; set; }
    public string Planet_Name { get; set; }
    public int Planet_X { get; set; }
    public int Planet_Y { get; set; }
    public string Planet_Desc { get; set; }

    public virtual ICollection<Mineral> Minerals { get; set; }
public class PlanetContext : DbContext
    public DbSet<Planet> Peoples { get; set; }

    public DbSet<Mineral> Minerals { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
            .HasMany(p => p.Minerals)
            .WithMany(m => m.Planets)
            .Map(t => t.MapLeftKey("PlanetID")

Updating multiple rows at once with Entity Framework

By : user7500596
Date : March 29 2020, 07:55 AM
will help you I am trying to figure out if there is a way to update multiple rows at once with Entity. , You should use the following concept to update multiple rows.
code :
using (var db = new MyDbContext())
var myData=db.YourTableObject.Where(x=>x.Someproperty=="Something").ToList();
myData.ForEach(m => m.YouPropertye= "Set Your Value",m.SomeOther="Set Other");

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