Entity Framework : CRUD Operations

Insert a row in database using EntityFramework 3.5

public abstract class EntityObject : StructuralObject, IEntityWithKey, IEntityWithChangeTracker, IEntityWithRelationships

{

      public EntityKey EntityKey { get; set; }

      public EntityState EntityState { get; }

      protected override sealed void ReportPropertyChanged(string property);

      protected override sealed void ReportPropertyChanging(string property);

}

Every object is derived from EntityObject type.
EntityKey ,
EntityState:Detached,Added,Deleted,Unchanged ;

the Entityset in storage model.

Delete in edm:

 Employees emp = entitycontext.Employees.FirstOrDefault(emps => emps.FirstName == "kasibabu");

 try

 {

           entitycontext.DeleteObject(emp); // gives error if emp is null.

           entitycontext.SaveChanges();

 }

catch (Exception)

 {

   Console.Write("object is not found");

              

 }                                    

First // FirstorDefault :

First---------> database must contains with the specified condition.
FirstOrDefault---> database may or may not satisfies condition.

Update in edm:

 Employees emp = entitycontext.Employees.First(emps => emps.FirstName == "kasi");

 emp.FirstName = "kasibabu";

 entitycontext.SaveChanges();

Update :

 Employees emp = entitycontext.Employees.First(emps => emps.FirstName == "kasi");

 emp.FirstName = "kasibabu";

 entitycontext.SaveChanges();

Note: for adding and deleteing object can be perform from EDM 4.0 onwords like below also

entitiycontext.Employee.AddObject(empobj);

and

entitycontext.Employee.DeleteObject(empobj);          

as well as

good explanation about  Entity Framework. and EF- about SSDL,CSDL,MSL

Entity framework has a conceptual model which is not directly linked to the domain model as in case of LINQ to SQL. This enables us to have a mapping layer in between the conceptual model and the persistent model. Entity framework uses 3 layers(EntityClient)

1. SSDL – Store schema definition language. This is the logical model which stores the database objects. This layer contains the Tables, Views, Stored Procedure, Functionsetc. These objects can be queried using SqlCommand, SqlConnection, SqlDataAdapteretc.
2. CSDL – Conceptual Schema definition language. This is the object model or the entity model that we use to query the data. This layer consists of Container, EntitySets, AssociationSets, AssociationTypes, Functions etc. These objects can be queried using an ADO.NET provider which exposes objects like EntityConnection, EntityCommand, EntityDataReader using a language called Entity SQL (ESQL).
3. MSL – Mapping Schema Language. This layer maps the conceptual model with the logical model. We use code attributes to map the conceptual model with the logical model. The following diagram taken from an MSDN article demonstrates the Architecture of Entity Framework.

as well as

at runtime based on the provider-->   SSDL

                                   SqlClient / OracleClient/ oledbClient...ect decided by EntityClient. makes connection

like

EntityConnection has a property ----> 

 EntityConnection:DbConnection

{

           public DbConnection StoreConnection { get; } // Storage Schema

}

StoreConnection : decides the derived type objects.
SqlConnection, SqlCommand,SqlDataAdapter............ect
or
OracleConnection,OracleCommand,OracleAdapter....ect

this DbConnection can be OracleConnection and SqlConnection.

SqlConnection : DbConnection, OracleConnection:DbConnection

like

based the stored connection which will connect to apporiate connection objects.

actuallly -->these  EntityConnection EntityCommand are works for

SqlConnection,SqlCommand.........ect.

every opertion(internally uses) is done through ADO.NET classes only.

NorthwindEntities context = new NorthwindEntities();

EntityConnection conn = new EntityConnection(context.Connection.ConnectionString);

            conn.Open();

var sql = "SELECT emp.LastName, emp.FirstName " +

                      "FROM NorthwindEntities.Employees AS emp";

 EntityCommand cmd = new EntityCommand(sql, conn);

DbDataReader reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);

            while (reader.Read())

            {

 Console.WriteLine("{0} {1}", reader["LastName"], reader["FirstName"]);

            }

as well

these classes are actually works with underlaying ADO.net classes like SQlconnection,SqlDataAdapter,SqlCommand...ect

these are hide by the Entity Framework---Storage Schema Implementation.

References:

http://www.nileshgule.com/2010/09/entity-framework-part-6-perform-crud.html
http://beaucrawford.net/post/Entity-Framework---Generating-SSDL2c-CSDL2c-and-MSL.aspx
http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2007/08/27/9611.aspx