logo
Tags down

shadow

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(),
});


Share : facebook icon twitter icon

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();
        db.WebSite_PermissionDB.Remove(validation);
        db.SaveChanges();
    }  
    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; }
    [Required]
    public string Name { get; set; }
    [Required]
    public string Symbol { get; set; }
    [Required]
    public string Mineral_Desc { get; set; }
    [Required]
    public int rate { get; set; }
    [Required]
    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; }
    [Required]
    public string Planet_Name { get; set; }
    [Required]
    public int Planet_X { get; set; }
    [Required]
    public int Planet_Y { get; set; }
    [Required]
    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)
    {
        modelBuilder.Entity<Planet>()
            .HasMany(p => p.Minerals)
            .WithMany(m => m.Planets)
            .Map(t => t.MapLeftKey("PlanetID")
                .MapRightKey("MineralID")
                .ToTable("PlanetMineral"));
    }
}

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");
db.SaveChanges()

}
Related Posts Related Posts :
  • How to get MacOS username in .NET Core console app?
  • How can I extract the first word of every line of a text file in C#
  • HttpClient isn't using Client Certificate for Mutual TLS Auth
  • How do I make a generic dictionary for multiple types implementing the same interface?
  • C# Form add controls on runtime
  • C# - program about while loop
  • Accessing variables in other Windows Form class C#
  • How to display tooltip / context menu from Run object in (wpf) RichTextBox
  • How to get a 0 before a datetime day when the day is below 10 in C#
  • Nothing shows when I tried to fill Combobox with .csv filenames
  • RSA Crypto: Is it require to store keypair after geneating first time
  • potential problems with c# with windows 7 due to .net versions
  • ASP.NET Core 2.1 RedirectToAction appends TempData to url
  • Random Number Generator using C#
  • Mixing MockVerify and FluentAssertions.Should() in C#
  • IdentityServer4 and Web Api in one project fails to authenticate
  • WebApi Core project debug is hanging on await client.GetAsync
  • Why can't I load System.Security.Cryptography.ProtectedData when it's on the same directory as the executable
  • Regular expression repeated sequence of characters
  • How to check all checkbox by pressing one?
  • Is it possible to use Plotly.js in a C# Winforms WebBrowser component?
  • Access to SelectedPath in Form2
  • IlGenerator Emit
  • How to remove initials from name using C#
  • .Net Core 2.2 / Kestrel / Swagger disabling Chunking / Encoding
  • Add comma in string if boolean is false
  • IComparable vs Equals() confused on which one to use
  • Pass object from DB to next page after listbox selection
  • Does Visual Studio 2015 Express for Desktop support JIT debugging?
  • How to properly add HttpRequestHeaders using system.net.http library
  • Calling MySQL Procedure is giving an exception that "procedure cannot be found"
  • Serialize and De-serialize XML with commented sections in C#
  • To update the field in database using Raw SQL?
  • Best way to unit test classes using streams?
  • JSON serialize list of object with listposition C#
  • WPF BIND Dynamically Image by Bitmap Resources
  • How to return a list of model items to an ASP.NET Core SelectListItem?
  • Get enum from specific number
  • Edit a file without changing it existing name
  • Remove from list items that have fields equal to some item fields
  • How to write OrderByDescending and where clause in single LinQ query
  • how to excute entity framework trace sql
  • how to write string array index in ravendb
  • How to update object stored inside an SQLite DB
  • Why does EF Core throws "Database already exists"?
  • Can we indexing all the fields in document in Elastic Search
  • Dynamics CRM products and bundles in a order
  • Unable to communitcate between two sibling containers
  • Filtering DataGridView via multiple combo boxes
  • How to Set data dynamic array From SQL in C#
  • How to retrieve Error Messages (server side) with field names?
  • Difference between "en-GB" and "en-Us" cultures names
  • Is there a way to loop through elements in c# wpf and connect them to a MySQL database?
  • Nested JSON from datatable and IList
  • SQL Bulk Insert in C# when you have GUID (UniqueIdentifier) Column
  • Set value to true if id is present in a string linq
  • Print Image to file using PrintDocument
  • Create a custom <Page> class derived from the WPF control in C#?
  • Custom classes in ASP.Net Core
  • How do I get the direction of a callout arrow on a msoShapeRoundedRectangularCallout?
  • shadow
    Privacy Policy - Terms - Contact Us © voile276.org