Entity Framework Difference vs3.5 sp1 and 4.0 ?

ObjectContext is more imporved in from Version of Entity Framework 4.0.

In case of 3.5 version -à No LazyLoadingEnabled support.

What is LazyloadingEnabled support?

In First Realise of EDM only current objects only loaded and referenced objects are not loaded.

EX:

using (NorthwindEntities context = new NorthwindEntities())

            {

                ObjectQuery<Products> products = context.Products;

                foreach (Products item in products)

                {

                       Console.WriteLine(item.ProductName);

                      Console.WriteLine(item.Categories.CategoryName);--NullRefrenceException                   

                      Console.Write(item.Discontinued + "\n");

                }

                Console.Read();

            }

 LazyLoading Support:  EF 4.0 onwords

ObjectContextOptions :

 LazyloadingEnable( default is falue). But while generating .edmx or EF generator automatically enables the Lazyloading is set to-àtrue.

public NorthwindEntities() : base("name=NorthwindEntities", "NorthwindEntities")

        {

             this.ContextOptions.LazyLoadingEnabled = true;

            OnContextCreated();

        }

   

  using (NorthwindEntities context=new NorthwindEntities())

            {

                ObjectSet<Product> products = context.Products;

                       foreach (Product item in products)

                       {

                           Console.WriteLine(item.ProductName);

                        Console.WriteLine(item.Category.CategoryName);--No Exception here

                           Console.Write(item.Discontinued +"\n");                                                      

                       }

                       Console.Read();

            }

Note: If we comment the    this.ContextOptions.LazyLoadingEnabled = true; // we can again NullRefrenceException.

ObjectQuery

Represents a query against the store. This query is formulated through an

Entity SQL statement, Query Builder methods, or Language-Integrated Query

(LINQ).

query against the store-àInstead Developer overhead of Entity-SQL. Prepared against the STORE

   using (NorthwindEntities context = new NorthwindEntities())

            {

                ObjectQuery<Products> Produt = context.Products;

                foreach (Products item in Produt)

                {

                    Console.WriteLine(item.ProductName);

//Console.WriteLine(item.Category.CategoryName);---not supported  3.5

                    Console.Write(item.Discontinued + "\n");

                }

                Console.Read();

            }

ObjectSet: 

This is also added in Entity Framework 4.0 onwords only. Which enable we can directly execute native commands (not required any Entity-SQL). In their databases.

ObjectSet :     Represents a typed Entity set to perform CRUD operations.

ObjectQuery<T>

  Represents a typed query against a conceptual model in a given object context.

Then

ObjectSet<TEntity> : ObjectQuery<TEntity>

Demo: 

using (NorthwindEntities context=new NorthwindEntities())

            {

                          ObjectSet<Product>   Produt=context.Products;

                          IQueryable<Product>   query =Produt.Where(s => s.CategoryID == 4);

                        foreach (Product item in query)

                        {

                            Console.WriteLine(item.ProductName);

                        }                                          

                       Console.Read();

            }

 which done through

Immediate window  :   code and config

code:

query.Provider--àtakes apporiate  Provider to execute the command.// Provider can be SqlClient,OracleClient….ect.

FROM: Northwind---open with xml

config

   <edmx:StorageModels>

      <Schema Namespace="NORTHWNDModel.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2005" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl">

……   </edmx:StorageModels>

NativeSQLCommad Execution.

  using (NorthwindEntities context=new NorthwindEntities())

            {

                        context.Connection.Open();

int Produt = context.ExecuteStoreCommand("update MyPerson set ssname='pavanisss' where pid=20", null);              

                       Console.Read();

            }

Stored Procedure execution is more simpler then compare to first  EDM.(vs 2008 sp1)

TotalProducts(conceptual name)----> totalproducts(acutal name sqlserver)

ObjectResult<Product> proudt=context.TotalProducts();  // exec totalproducts

foreach (Product item in proudt)

{

        Console.WriteLine(item.ProductName);

        Console.WriteLine(item.Category.CategoryName);

        Console.WriteLine(item.Supplier.CompanyName);

}

                                Incae of  Stored Procedure Requeries Parameters : 

       ObjectResult<Product> proudt=context.ByProductName("Chai");;  // exec totalproducts

foreach (Product item in proudt)

{

        Console.WriteLine(item.ProductName);

        Console.WriteLine(item.Category.CategoryName);

        Console.WriteLine(item.Supplier.CompanyName);

}

Designer automatically generates Object parameters:

  public ObjectResult<Product> ByProductName(global::System.String productname)

        {

            ObjectParameter productnameParameter;

            if (productname != null)

            {

                productnameParameter = new ObjectParameter("productname", productname);

            }

            else

            {

                productnameParameter = new ObjectParameter("productname", typeof(global::System.String));

            }

   

            return base.ExecuteFunction<Product>("ByProductName", productnameParameter);

        }

In case of Stored Parameters returns 
 Complex types(anamouns type): few columns only.

then we uses this complex type in code 

VS3.5sp1: ObjectContext

vs 2010(.net 4.0) ObjectContext

Adding New Object :

using (NorthwindEntities context=new NorthwindEntities())

            {

                Student sobj = new Student { sname = "babu", sloc = "hyd" };

                context.Students.AddObject(sobj);

                context.SaveChanges();                     

                       Console.Read();

            }

Delete a object :

  using (NorthwindEntities context=new NorthwindEntities())

            {

                Student sobj = context.Students.First(i => i.sname == "babu");

                context.Students.DeleteObject(sobj);

                context.SaveChanges();                     

                       Console.Read();

            }