#entity framework core

本篇文將介紹用Visual Studio 在Web應用程式專案，如何去使用 Entity Framework Core 去做CRUD

Tablo tanımlarını yaptıktan sonra çalıştırılan kodlar alttaki gibidir.

Nuget terminal komutları;

Add-Migration Initial

Update-Database Gerekli Nuget paketler;

Microsoft.EntityFrameworkCore.Tools

Microsoft.EntityFrameworkCore.Design

So Entity Framework Core doesn't support lazy loading of navigational properties. This isn't the worst thing in the world, but it does become a bit of a problem when given this fact:

If you change the query so that it no longer returns instances of the entity type that the query began with, then the include operators are ignored.

From the MS docs:

In the following example, the include operators are based on the Blog, but then the Select operator is used to change the query to return an anonymous type. In this case, the include operators have no effect.

using (var context = new BloggingContext()) { var blogs = context.Blogs .Include(blog => blog.Posts) .Select(blog => new { Id = blog.BlogId, Url = blog.Url }) .ToList(); }

So now, because of this, I have this monstrosity of a query:

var submissions = await _db.Submissions .Include(x => x.answers) .ThenInclude(x => x.question) .Include(x => x.answers) .ThenInclude(x => x.answer) .Include(x => x.answers) .ThenInclude(x => x.cardchoices) .ThenInclude(x => x.card) .Include(x => x.answers) .ThenInclude(x => x.choiceanswers) .ThenInclude(x => x.answer) .Where(x => x.surveyid == id) .Where(x => x.answers.Any()) .Select(x => x.answers .OrderBy(y => y.question.sortorder) .Select(y => new { question = y.question.sortorder, answer = y.answer.text, text = y.text, cards = string.Join(", ", y.cardchoices.Select(z => z.card.gameid)), selections = y.choiceanswers.Select(z => z.answer) }) ) .ToListAsync();

public abstract class Common { public int id { get; set; } public DateTime created { get; set; } public string createdby { get; set; } public DateTime modified { get; set; } public string modifiedby { get; set; } }

and then all of my classes inherit from that one. The thing is, manually updating those four properties on every write to the database is, let's face it, a pain. So during my trials with entity framework core 2.0, I stumbled across a stack overflow post which pointed me at the following code:

public override Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken)) { var changeSet = ChangeTracker.Entries<Common>(); if (changeSet != null) { foreach (var entry in changeSet.Where(x => x.State != EntityState.Unchanged)) { if (entry.State == EntityState.Added) { entry.Entity.created = DateTime.Now; entry.Entity.createdby = user; } entry.Entity.modified = DateTime.Now; entry.Entity.modifiedby = user; } } return base.SaveChangesAsync(cancellationToken); }

Getting Started with Entity Framework Core

In this article you will learn about new lightweight version of entity framework that is entity framework core . If you have entity framework experience , you may be aware that EF core has been written from scratch to achieve some new goals Here you will learn about similarities and differences from EF 6

So What is Entity Framework ?

Entity framework is the set of .net APIs for performing data…

Using Enums as database keys [Primary $ Foreign] in C# and EF Core

Do not use the exact name of the Enum (add number or underscore)

Snippet

Snippet

public enum InvoiceFor     {         PremiumPackage = 1,         BasicPackage = 2,         AutoSetup = 5,         PinNewsOffer = 6,         PinNewMember = 7     } Snippet

public class PaymentPackage     {         [Key]         public InvoiceFor _InvoiceFor { get; set; }         public string Paypal { get; set; }…

Top 5 new features of Entity Framework Core 1.0

In this article, we will learn the top 5 new features of Entity Framework Core.

  EF Core is an object-relational mapper (O/RM) that enables .NET developers to work with a database using .NET objects. It eliminates the need for most of the data-access code that developers usually need to write. We will discuss top 5 new features of Entity Framework Core here.  

1. Cross Platform Support:

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