LazyloadingEnable and ProxyCreationEnabled?

yes, lazyloadingEnable and ProxyCreationEnabled are by default true. yes using lazyloading should be true for referencing the reference tables.
so

            this.Configuration.LazyLoadingEnabled = true;

           this.Configuration.ProxyCreationEnabled = true;

           

both must be enabled true otherwise gives error. bydefault LazyLoadingEnabled is true because of all the related entities are loaded automatically.

           

   var t = context.emps.Find(4);

as well

if any case : 

  this.Configuration.ProxyCreationEnabled = false; 

                also we can load the relavent entities using 

   var t = context.emps.Find(4);

   context.Entry(t).Reference("Dept").Load();  // Proxy Creation

  or

  context.Entry(t).Reference(t=>t.Dept).Load(); // here Dept can't be a non-generic collection.

     var s  =context.emps.Local;

    context.emps.Add(new Employee { Ename = "rani", EPhone = "7478", EmpDept = 2 });

    context.SaveChanges();

             

using local properties we can able to track the changes at client when we add, delete, ...from a collection why because Local is Property which is of

ObservableCollection<TEntity> Local { get; }.

   var s  =context.emps.Local;  // Local return type is ObservableCollection. so we can easily track the changes of a collection at dynamically.

  context.emps.Add(new Employee { Ename = "rani", EPhone = "7478", EmpDept = 2 });  //1

               var  d = context.emps.FirstOrDefault(k => k.Ename == "narayan");

               d.Ename = "prasads";                                                //2

IEnumerable<DbEntityEntry<Employee>> change =context.ChangeTracker.Entries<Employee>();

               IEnumerator<DbEntityEntry<Employee>> ier = change.GetEnumerator();

               IEnumerable<string> currentval = new List<string>();

               IEnumerable<string> original = new List<string>();

               while (ier.MoveNext())

               {

                    currentval=ier.Current.CurrentValues.PropertyNames;

                    original=ier.Current.OriginalValues.PropertyNames;

               }

immediate window

change.count()

2

context.emps.Local[0]

{EFCodeFirstDemo.Employee}

    Dept: null

    Eid: 0

    EmpDept: 2

    Ename: "rani"

    EPhone: "7478"

How CodeFirst default LazyloadingEnable is true ?

Yes, using Include also we can retrive the relavent data using Navigation Property,but which excepts a navigation property. like

   public class Employee

    {

        [Key]

        public int Eid { get; set; }

        public string Ename { get; set; }

        public string EPhone { get; set; }

        public int EmpDept { get; set; }     

        public virtual Departments   Dept { get; set; }  // Navigation Property

    }

    public class Departments

    {

        [Key]

        public int Did { get; set; }

        public string DName { get; set; }   

    }

    public class Conn : DbContext

    {

        public DbSet<Employee> emps { get; set; }

        public DbSet<Departments> depts { get; set; }    

        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

            modelBuilder.Entity<Employee>()

               .HasRequired(a => a.Dept)

               .WithMany()

               .HasForeignKey(u => u.EmpDept);

            base.OnModelCreating(modelBuilder);

        }

   

    }

then

-----

class Program

    {

        static void Main(string[] args)

        {

        Conn context = new Conn();

         Employee eobj = new Employee { Ename = "France", EPhone = "7176", EmpDept = 2 };

            context.emps.Add(eobj);

            context.SaveChanges();

        }

   }

thin Executed in DAtabase

Eid          Ename        EPhone                EmpDept             Did         DName

1              raju            7171                          1              1              Accounts

2              naveen        7172       2              2              Business

3              Chaitanya     7173          1              1              Accounts

4              Dinesh       7174       2              2              Business

5              Eswar     7175       3                3              DBA

6              France      7176       2                2              Business

  IQueryable<Employee> 

t = context.emps.Include("Dept").Where(n => n.Ename == "raju").Select(n => n);

immediate window

t

SELECT 

[Extent1].[Eid] AS [Eid], 

[Extent1].[Ename] AS [Ename], 

[Extent1].[EPhone] AS [EPhone], 

[Extent1].[EmpDept] AS [EmpDept], 

[Extent2].[Did] AS [Did], 

[Extent2].[DName] AS [DName]

FROM  [dbo].[Employees] AS [Extent1]

INNER JOIN [dbo].[Departments] AS [Extent2] ON [Extent1].[EmpDept] = [Extent2].[Did]

WHERE N'raju' = [Extent1].[Ename]

Eid Ename EPhone EmpDept Did DName

1 raju 7171 1 1 Accounts

6 raju 7176 2 2 Business

emps------------> select * from emp

here where is department details?
so by default lazyloading is enabled but as per quering the data base only which returns now.
which will generates.

as well as

    public class Departments

    {

        [Key]

        public int Did { get; set; }

        public string DName { get; set; }

        public virtual ICollection<Employee> DeptEmployees { get; set; }

    }

now we can insert multiple employee records
as well as
we can retrive multiple employee records also. as a collections

how to insert multiple records:

   Employee emp = new Employee { Ename = "narayanarao", EPhone = "7175" };

                Employee emp1=new Employee{ Ename="shekar", EPhone="7176"};

                List<Employee> elist=new List<Employee>();

                elist.Add(emp);

                elist.Add(emp1);

                Departments d = new Departments { DeptEmployees = elist, DName="Professionals" };

                context.depts.Add(d);

                context.SaveChanges();

how to retrive particular dept records :

  var t = context.depts.Include("DeptEmployees");           //     DeptEmployees 

                foreach (var item in t)

                {

          ICollection<Employee> ems = item.DeptEmployees;  // grouped by department id

                    foreach (var items in ems)

                    {

                        Console.WriteLine(items.Ename);

                        Console.WriteLine(item.DName);

                    }

                }

Note:   DeptEmployees  column is  created at Employee table why because to this column referenceing the apporiate Employee.

Columns:


EmpDept----particular employee

Departments_Did-----collection of employees/ a particular dept employees

Code First: Queries, Stored Procedures

Yes, till now we created 2 POCO Classes(Employee,Departments) then we seen how to perform Crud Operations.

but now we will see How to Enable 

Using queries:

POCO Class is  Employee then but which is saved in database as Employees---> s is added to every  POCO class in Code First model

like : Employee--Employees, Dept---Depts....ect

DbSqlQuery<Employee> employees = context.emps.SqlQuery("SELECT * FROM dbo.Employees");//.ToList();

                foreach (Employee item in employees)

                {

                    Console.WriteLine(item.EPhone);

                   

                }

Using StoredProcedure:

ALTER PROCEDURE [dbo].[stp_InsertEmp]

(

      @Name as VARCHAR(50),

    @Phone as Varchar(50),

    @Eaddress as int

) AS

 begin

INSERT INTO dbo.Employees(EName,EPhone,Eaddress)VALUES(@Name,@Phone,@Eaddress)

end

                               ===============================

    public class Conn : DbContext

    {

            public DbSet<Employee> emps { get; set; }

            public DbSet<Departments>  dept{ get; set; }

         public void AddEmp(Employee emp)

        {

            SqlParameter[] pars=new SqlParameter[3];

            pars[0]=new SqlParameter("@Name",emp.Ename);

            pars[1]=new SqlParameter("@Phone", emp.EPhone);

            pars[2]=new SqlParameter("@Eaddress",emp.Eaddress);

        base.Database.ExecuteSqlCommand("exec stp_InsertEmp @Name,@Phone,@Eaddress", pars);

       

        }

 }

  Conn context = new Conn();
{

           

Employee eobj = new Employee { Dept = new Departments { DName = "Dept2" }, Ename = "James", EPhone = "7744", Eaddress = 1 };

         

            context.AddEmp(eobj);

            Console.WriteLine("Saved Succesully ...storedprocedure");

           

}

ALTER procedure [dbo].[SelectEmp]

@eids int

as

begin

select * from dbo.Employees where EId=@eids

end

using (Conn  context= new Conn())

 {

            

 IList<Employee> emplist;

              

      sqlParameter categoryParam = new SqlParameter("@eids",7);

emplist = context.Database.SqlQuery<Employee>("exec SelectEmp @eids", categoryParam).ToList();

                    foreach (Employee item in emplist)

                    {                       

                        Console.WriteLine(item.Ename);

                        Console.WriteLine(item.Eaddress);

                    }

                    Console.ReadKey();

                }

Ex :


 DbSet<Employee> t = context.emps;

                Employee e= t.Find(1);

immediate window:


e.EmpDept
1
e.Ename
"raju"
e.Dept.DName
"Accounts"

            
Ex:


Employee t = context.emps.Find(4);--------single record along with dept details

t

    Dept: {EFCodeFirstDemo.Departments}

    Eid: 4

    EmpDept: 2

    Ename: "Dinesh"

    EPhone: "7174"

t.Dept.DName

"Business"

How to Creating in-memory object(Employee --> t)  ?

using create() method

            Conn context = new Conn();

        

            Employee t = context.emps.Create();

            t.Ename = Console.ReadLine();

            t.EPhone = Console.ReadLine();

            t.EmpDept = Convert.ToInt32(Console.ReadLine());          

            context.emps.Add(t);

            context.SaveChanges();

                 

Code First mappings using Fluent API

yes, previously we uses EF-Code first classes then we mapping between the POCO classes in code-first model

but using Fluent -API automatics this connvation. which will minizes coding

public class Conn : DbContext

    {

        public DbSet<Employee> emps { get; set; }

        public DbSet<Departments>  dept{ get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)

        {

               //  modelBuilder.Entity<Employee>()               //.HasRequired(a => a.Dept)

               //.WithMany()                   

               //.HasForeignKey(u => u.Eaddress);

            //modelBuilder.Entity<Employee>().

                              

           // base.OnModelCreating(modelBuilder);

            //      or

             

            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

        }

    }

Reference : http://msdn.microsoft.com/en-us/data/jj591620

http://blogs.msdn.com/b/aspnetue/archive/2011/05/04/entity-framework-code-first-tutorial-supplement-what-is-going-on-in-a-fluent-api-call.aspx

How to write Relationships in Code First?

Yes, Code First Entity Framewok supports relationships like Database First/Relational databases now

Entities :

public class Employee

    {

        [Key]

        public int Eid { get; set; }

        public string Ename { get; set; }

        public string EPhone { get; set; }

        public int Eaddress { get; set; }     

        public Departments Dept { get; set; }

    }

    public class Departments

    {

        [Key]

        public int Did { get; set; }

        public string DName { get; set; }

    }

Here:

Departments----PK table

Employee----Fk table

Primary keys are autogenerated if we send also those are ignored.

Eaddress(reference Departments)à is a reference key of Departments table.  as well we can specify the Department also at a time

Ex:

   Employee eobj = new Employee { Dept = new Departments { DName = "Accounts" },

            Ename = "raju", EPhone = "7171" };

            con.emps.Add(eobj);

            con.SaveChanges();

 

Eid          Ename  EPhone                Eaddress

1              raju        7171       1

Did         DName

1                     Accounts

Employee is automatically mapped to dept of 1

  Employee eobj = new Employee {  Eaddress=1, Ename = "raju1", EPhone = "7172" };

What is use of   public int Eaddress { get; set; }      in Employee ?

New employee -----belongs to existing Department.

Eid          Ename  EPhone                Eaddress

1              raju        7171       1

2              raju1      7172       1  // newly employee added to  existing department.

Did         DName

1                     Accounts

And

We can add new Department aswell new employee at a time.

    Employee eobj = new Employee { Dept = new Departments { DName = "Sales" }, Ename = "balu", EPhone = "4131" };

Eid          Ename  EPhone                Eaddress

1              raju        7171       1

2              raju1      7172       1

3              balu       4131       2

Belongs

Did         DName

1              Accounts

2              Sales

 how to specify keys in Code-First model:

             modelBuilder.Entity<Employee>()

               .HasRequired(a => a.Dept)

               .WithMany()                     --à type of relationship

               .HasForeignKey(u => u.Eaddress);

            //modelBuilder.Entity<Employee>().

                              

            base.OnModelCreating(modelBuilder);

NOTE: keep in mind -à data will be splicted as per columns and stored in their relavent tables.