Uvod u Entity Framework 6

KORAK 1: Dodavanje ADO.NET Entity Data Model-a
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1. Desni klik na projekat (u Solution Explorer)
2. Add → New Item...
3. U prozoru "Add New Item":
   - Odaberite kategoriju: Data
   - Odaberite template: ADO.NET Entity Data Model
   - Name: StateStatisticsModel.edmx
   - Kliknite "Add"

KORAK 2: Izbor Pristupa (Entity Data Model Wizard)
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U "Choose Model Contents" dijalogu:
├─○ EF Designer from database ← ODABERITE OVO za Database-First
├─○ Empty EF Designer model
├─○ Empty Code First model
└─○ Code First from database

Kliknite "Next"

KORAK 3: Konekcija na Bazu
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U "Choose Your Data Connection" dijalogu:

A) AKO NEMATE POSTOJEĆU KONEKCIJU:
   1. Kliknite "New Connection..."
   2. U "Choose Data Source":
      - Data source: Microsoft SQL Server
      - Data provider: .NET Framework Data Provider for SQL Server
      - Kliknite "Continue"
   3. U "Connection Properties":
      - Server name: (LocalDb)\MSSQLLocalDB    // za LocalDB
      - ili: .\SQLEXPRESS                      // za SQL Express
      - ili: sql-server.vlada.local            // za production
      - Authentication: Windows Authentication  // PREPORUČENO
      - Select database: StateStatisticsDB
      - Kliknite "Test Connection" - treba pokazati "Test connection succeeded."
      - Kliknite "OK"

B) AKO IMATE POSTOJEĆU KONEKCIJU:
   1. Odaberite iz dropdown liste
   2. Provjerite "Save connection settings in Web.config as:"
      - Ime: StateStatisticsDBEntities (EF dodaje "Entities" sufiks)
   
Kliknite "Next"

KORAK 4: Izbor EF Verzije
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U "Choose Your Version" dijalogu:
- Odaberite: Entity Framework 6.x
Kliknite "Next"

KORAK 5: Izbor Database Objekata
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U "Choose Your Database Objects and Settings" dijalogu:

✅ Tables
   └─ ✅ Stats (schema)
         ├─ ✅ Departments
         ├─ ✅ Employees
         ├─ ✅ Managers
         ├─ ✅ Projects
         └─ ✅ ProjectEmployees

□ Views (opciono - možete odabrati)
□ Stored Procedures and Functions (opciono)

Opcije (VAŽNO):
✅ Pluralize or singularize generated object names
   (Department klasa = Departments tabela, automatski)
✅ Include foreign key columns in the model
   (Uključuje DepartmentID u Employee klasu)
□ Import selected stored procedures and functions into the entity model

Model Namespace: StateStatisticsModel

Kliknite "Finish"

KORAK 6: Generisanje
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Visual Studio će:
1. Kreirati .edmx fajl
2. Generisati sve Model klase
3. Generisati DbContext klasu
4. Dodati connection string u Web.config
5. Dodati EntityFramework NuGet package (ako već nije)

⏳ Proces traje 5-30 sekundi zavisno od veličine baze.

// --------------------------------------------------
// AUTO-GENERATED - NE EDITUJTE DIREKTNO!
// Regeneriše se svaki put kad update-ujete model iz baze
// --------------------------------------------------

namespace JavnaUprava.Models
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;
    
    // Napomena: Ime klase dolazi iz "Model Namespace" u wizard-u
    public partial class StateStatisticsDBEntities : DbContext
    {
        // Konstruktor - koristi connection string name iz Web.config
        // "name=StateStatisticsDBEntities" znači traži  u Web.config
        public StateStatisticsDBEntities()
            : base("name=StateStatisticsDBEntities")
        {
        }
    
        // DbContext konfigurisanje konekcije
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // EF automatski poziva ovu metodu pri inicijalizaciji
            // Database-First OBIČNO ne dodaje ništa ovdje jer sve čita iz .edmx fajla
            throw new UnintentionalCodeFirstException();
        }
    
        // DbSet za svaku tabelu koju ste odabrali u wizard-u
        // EF pluralizuje imena: Departments (tabela) → Departments (DbSet)
        public virtual DbSet<Department> Departments { get; set; }
        public virtual DbSet<Employee> Employees { get; set; }
        public virtual DbSet<Manager> Managers { get; set; }
        public virtual DbSet<Project> Projects { get; set; }
        
        // Junction tabela - EF automatski kreira many-to-many relaciju
        public virtual DbSet<ProjectEmployee> ProjectEmployees { get; set; }
    }
}

// --------------------------------------------------
// AUTO-GENERATED IZ BAZE: StateStatisticsDB.Stats.Departments
// --------------------------------------------------

namespace JavnaUprava.Models
{
    using System;
    using System.Collections.Generic;
    
    // partial omogućava vam da dodajete custom kod u zasebnom fajlu
    public partial class Department
    {
        // Konstruktor - EF kreira praznu kolekciju za navigation properties
        // Ovo sprječava NullReferenceException kada pristupate dept.Employees
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Department()
        {
            this.Employees = new HashSet<Employee>();
            this.Managers = new HashSet<Manager>();
        }
    
        // Primary key - EF detektuje iz baze (IDENTITY column)
        public int DepartmentID { get; set; }
        
        // NOT NULL columns postaju required properties
        public string DepartmentName { get; set; }
        
        // NULLABLE columns postaju nullable properties
        public string DepartmentCode { get; set; }
        
        // decimal(18, 2) u SQL → decimal u C#
        public decimal Budget { get; set; }
        
        // Navigation Properties - EF generiše na osnovu Foreign Key relacija
        // virtual omogućava Lazy Loading (učitavanje po potrebi)
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Employee> Employees { get; set; }
        
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Manager> Managers { get; set; }
    }
}

// Models/JavnaUpravaDbContext.cs
using System.Data.Entity;

namespace JavnaUprava.Models
{
    public class JavnaUpravaDbContext : DbContext
    {
        // Konstruktor - prima connection string ime iz Web.config
        public JavnaUpravaDbContext() 
            : base("StateStatisticsDB")
        {
        }

        // DbSet predstavlja kolekciju entiteta u bazi
        public DbSet<Department> Departments { get; set; }
        public DbSet<Employee> Employees { get; set; }
        public DbSet<Project> Projects { get; set; }

        // OnModelCreating - za konfiguraciju modela
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // Konfiguracija Stats sheme (jer koristimo postojeću bazu)
            modelBuilder.Entity<Department>().ToTable("Departments", "Stats");
            modelBuilder.Entity<Employee>().ToTable("Employees", "Stats");
            modelBuilder.Entity<Project>().ToTable("Projects", "Stats");
            
            base.OnModelCreating(modelBuilder);
        }
    }
}

// Models/Department.cs
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace JavnaUprava.Models
{
    [Table("Departments", Schema = "Stats")]
    public class Department
    {
        [Key]
        public int DepartmentID { get; set; }
        
        [Required]
        [StringLength(100)]
        public string DepartmentName { get; set; }
        
        [StringLength(20)]
        public string DepartmentCode { get; set; }
        
        public decimal Budget { get; set; }
        
        // Navigation property - kolekcija zaposlenika
        public virtual ICollection<Employee> Employees { get; set; }
    }
}

// Models/Employee.cs
namespace JavnaUprava.Models
{
    using System;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;

    [Table("Employees", Schema = "Stats")]
    public class Employee
    {
        [Key]
        public int EmployeeID { get; set; }
        
        [Required]
        [StringLength(50)]
        public string FirstName { get; set; }
        
        [Required]
        [StringLength(50)]
        public string LastName { get; set; }
        
        [Required]
        [StringLength(13)]
        public string JMBG { get; set; } // Specifično za javnu upravu
        
        // Foreign key
        public int DepartmentID { get; set; }
        
        // Navigation property
        public virtual Department Department { get; set; }
    }
}

1. Desni klik na projekat → Manage NuGet Packages
2. Pretražite "EntityFramework"
3. Odaberite "EntityFramework" (verzija 6.4.4 ili novija)
4. Kliknite "Install"

Alternativno, koristite Package Manager Console:
PM> Install-Package EntityFramework

public class Department 
{
    public int DepartmentID { get; set; }
    public string Name { get; set; }
    
    // Parent klasa sadrži ICollection (listu) dječijih entiteta.
    // Oznaka VIRTUAL omogućava funkciju "Lazy Loading" (učitavanje na zahtjev).
    public virtual ICollection<Employee> Employees { get; set; }
}

public class Employee 
{
    public int EmployeeID { get; set; }
    public string FullName { get; set; }
    
    // Child klasa sadrži Foreign Key (opciono ali snažno preporučeno zbog obrade u Views-ima)
    public int DepartmentID { get; set; }
    
    // Obavezna referenca na instancu parenta
    public virtual Department Department { get; set; }
}

public class Employee 
{
    public int EmployeeID { get; set; }
    // Radnik je angažovan na više projekata istovremeno
    public virtual ICollection<Project> Projects { get; set; }
}

public class Project 
{
    public int ProjectID { get; set; }
    public string ProjectName { get; set; }
    // Na jednom projektu radi više radnika
    public virtual ICollection<Employee> Employees { get; set; }
}

public class Employee 
{
    public int EmployeeID { get; set; }
    
    // Reference na child komponentu
    public virtual HealthRecord HealthRecord { get; set; } 
}

public class HealthRecord 
{
    // Key istovremeno služi i kao PK (u svojoj tabeli) i kao FK prema Employee tabeli
    [Key, ForeignKey("Employee")]
    public int EmployeeID { get; set; }
    public string BloodType { get; set; }
    
    // Reference na parenta
    public virtual Employee Employee { get; set; }
}