1. © Satyam Computer Services Ltd. 2008 POC Architecture 1 Confidential – Limited Circulation

2. © Satyam Computer Services Ltd. 2008 Agenda LINQ TO SQL  Architecture  Objects in LINQ-TO-SQL  Examples  Transactions  POC Demo 2

3. © Satyam Computer Services Ltd. 2008 3 Confidential – Limited Circulation LINQ -TO - SQL

4. © Satyam Computer Services Ltd. 2008 What is LINQ-TO-SQL? 4 Confidential – Limited Circulation  Provides a runtime infrastructure for managing relational data as objects without losing the ability to query.  Application is free to manipulate the objects while LINQ to SQL stays in the background tracking your changes automatically  Objects linked to relational data can be defined just like normal objects, only decorated with attributes to identify how properties correspond to columns.  Together, the LINQ to SQL run-time infrastructure and design-time tools significantly reduce the workload for the database application developer.

5. © Satyam Computer Services Ltd. 2008 LINQ Architecture 5 Confidential – Limited Circulation LINQ-enabled data sources LINQ To Objects LINQ LINQ To XML LINQ LINQ-enabled ADO.NET Visual Basic OthersOthers LINQ To Entities LINQ LINQ To SQL LINQ LINQ To Datasets LINQ.Net Language Integrated Query (LINQ) Visual C# Objects XMLXML Databases

6. © Satyam Computer Services Ltd. 2008 LINQ TO SQL Architecture 6 Confidential – Limited Circulation ApplicationApplication LINQ to SQL SQL Server from d in db.Doctors where d.City == “Bangalore" select c.doctorName from d in db.Doctors where d.City == “Bangalore" select c.doctorName Enumerate SELECT doctorName FROM Doctors WHERE City = ‘Bangalore' SELECT doctorName FROM Doctors WHERE City = ‘Bangalore' SQL query or stored proc Rows Objects Db.Doctors.Add(d1); c2.City = “bangalore”; db.Doctors.Remove(d3); Db.Doctors.Add(d1); c2.City = “bangalore”; db.Doctors.Remove(d3); SubmitChanges() INSERT INTO Doctors … UPDATE Doctors … DELETE FROM Doctors … INSERT INTO Doctors … UPDATE Doctors … DELETE FROM Doctors … DML or SProcs

7. © Satyam Computer Services Ltd. 2008 Benefits 7 Confidential – Limited Circulation  Traditionally, queries against data are expressed as simple strings without type checking at compile time or IntelliSense support.  We can write queries against strongly typed collections of objects by using language keywords and familiar operators.  LINQ applies the principles of object-oriented programming to relational data.  It provides a unified programming model for querying data from different types of Data sources, XML documents, ADO.NET Datasets, and any collection of objects that supports Ienumerable  LINQ-enabled languages can provide full type-safety and compile-time checking of query expressions, and development tools can provide full intellisense, debugging  Fully supports transactions, views, and stored procedures.

8. © Satyam Computer Services Ltd. 2008 Entity Classes 8 Confidential – Limited Circulation Apply a custom attribute to the top of the class declaration. LINQ to SQL defines the Table attribute for this purpose. Example: [Table(Name="Customers")] public class Customer { [Column(Storage=“_Cust_Id",DbType="Int NOT NULL“,IsPrimaryKey=true)] public string CustomerID; [Column(Storage="_City",DbType=“VarChar(50) NOT NULL")] public string City; }

9. © Satyam Computer Services Ltd. 2008 Data Context 9 Confidential – Limited Circulation  A channel or platform by which you retrieve objects from the database and resubmit changes  It is initialized with a connection or connection string  Purpose of the DataContext is to translate your requests for objects into SQL queries made against the database and then assemble objects out of the results. public partial class Northwind : DataContext { public Table Customers; public Table Orders; public Northwind(string connection): base(connection) {} }

10. © Satyam Computer Services Ltd. 2008 Data Context Examples 10 Confidential – Limited Circulation // DataContext takes a connection string DataContext db = new DataContext("c:\\northwind\\northwnd.mdf"); // Get a typed table to run queries Table Customers = db.GetTable (); // Query for customers from London var q = from c in Customers where c.City == "London" select c; foreach (var cust in q) Console.WriteLine("id = {0}, City = {1}", cust.CustomerID, cust.City);

11. © Satyam Computer Services Ltd. 2008 Relationships 11 Confidential – Limited Circulation  LINQ to SQL defines an Association attribute you can apply to a member used to represent a relationship.  An association relationship is one like a foreign-key to primary-key relationship that is made by matching column values between tables.

12. © Satyam Computer Services Ltd. 2008 Relationships(Master Table) 12 Confidential – Limited Circulation [Table(Name="City")] public class City { [Column(Id=true)] public int city_ID;... private EntitySet _Doctors; [Association(Storage="_Doctors", OtherKey="city_id")] public EntitySet Doctors { get { return this.Doctors; } set { this.Doctors.Assign(value); } }

13. © Satyam Computer Services Ltd. 2008 Relationships (Child Table) 13 Confidential – Limited Circulation [Table(Name="Doctors")] public class Doctor { [Column(Id=true)] public int doctorID; [Column] public string city_ID; private EntityRef _city; [Association(Storage="_city", ThisKey="cityID")] public Customer Customer { get { return this._city.Entity; } set { this._city.Entity = value; } }

14. © Satyam Computer Services Ltd. 2008 LINQ Query Examples 14 Confidential – Limited Circulation public class Doctor { … } public class DBHelperDataContext: DataContext { public Table Doctors; … } public class Doctor { … } public class DBHelperDataContext: DataContext { public Table Doctors; … } DBHelperDataContext db = new DBHelperDataContext(…); var contacts = from d in db.Doctors where d.City == “London" select new { d.doctorName }; DBHelperDataContext db = new DBHelperDataContext(…); var contacts = from d in db.Doctors where d.City == “London" select new { d.doctorName }; Classes describe data Strongly typed connections Integrated query syntax Strongly typed results Tables are like collections

15. © Satyam Computer Services Ltd. 2008 Query Examples 15 Confidential – Limited Circulation Ex 1: var q = from c in db.city from d in c.Doctors where c.City == “Bangalore" select new { c, d }; Ex 2: var q = from d in db.Doctors where d.city.cityName == "London" select new { c = d.Doctors, d };

16. © Satyam Computer Services Ltd. 2008 Query Examples 16 Confidential – Limited Circulation Ex: 4 var q = from d in db.Doctors where d.City == “London" select d; foreach (Doctor d in q) Console.WriteLine(d.doctorName); The actual type of q in this instance is IQueryable. It's not until the application attempts to enumerate the contents of the query that it actually executes. In this example the foreach statement causes the execution to occur.

17. © Satyam Computer Services Ltd. 2008 Query Examples 17 Confidential – Limited Circulation var q = from d in db.Doctors Where d.city == ‘Bangalore’ Select d; foreach (Doctor d in q) { if (d.Speciality ==‘ENT’) getAppointment(d.Doctor); }

18. © Satyam Computer Services Ltd. 2008 Deferred Execution 18 Confidential – Limited Circulation \\Each foreach causes the SQL to be \\executed var q = from d in db.Doctors Where d.City == “London" select d; foreach (Doctor d in q) Console.WriteLine(d.doctorName); foreach (Doctor d in q) Console.WriteLine(d.CompanyName); var q = from d in db.Doctors Where d.City == “London" select d; // Execute once using ToList() or //ToArray() var list = q.ToList(); foreach (Doctor d in list) Console.WriteLine(d.doctorName); foreach (Doctor d in list) Console.WriteLine(d.CompanyName); Actual SQL query is executed when foreach statement is executed

19. © Satyam Computer Services Ltd. 2008 Deferred Execution Benefits 19 Confidential – Limited Circulation var q = from d in db.Doctors where d.City == "London" select d; if (orderByLocation) { q = from d in q orderby d.Country, d.City select d; } else if (orderByName) { q = from d in q orderby d.DoctorName select d; } foreach (Doctor d in q) Console.WriteLine(d.DoctorName);

20. © Satyam Computer Services Ltd. 2008 Object Identity 20 Confidential – Limited Circulation DataContext manages object identity.  Whenever a new row is retrieved from the database, it is logged in an identity table by its primary key and a new object is created.  Whenever that same row is retrieved again, the original object instance is handed back to the application.  In this way, the DataContext translates the databases concept of identity (keys) into the languages concept (instances).  In the case that the database contains a table without a primary key, LINQ to SQL allows queries to be submitted over the table, but it doesn't allow updates.

21. © Satyam Computer Services Ltd. 2008 DML Operations 21 Confidential – Limited Circulation Inserting InsertOnSubmit(entity) InsertAllOnSubmit(entityCollection) Constraints are not checked early, queries are always sent to the database. Updating SubmitChanges() Deleting DeleteOnSubmit(entity) DeleteAllOnSubmit(entityCollection)

22. © Satyam Computer Services Ltd. 2008 Updating Data 22 Confidential – Limited Circulation After SubmitChanges() is called  Modified objects in the object graph are identified.  New objects to be inserted  Retrieved objects to be deleted  Retrieved objects whose persistent members have changed  Changes are ordered based on foreign key constraints.  Insert, update and delete statements are constructed with modified current values in the set clause and original values in the where clause for optimistic concurrency conflict detection  Database connection is opened and a transaction is started. If there are any errors, the transaction is rolled back. If the transaction succeeds, the internal state of the DataContext is changed accordingly. Database-generated columns like autoincrement / GUID keys and timestamps are propagated back to the objects

23. © Satyam Computer Services Ltd. 2008 Exception Handling 23 Confidential – Limited Circulation DBHelperdataContext db = new DBHelperdataContext(); // make changes here try { db.SubmitChanges(); } catch (Exception e) { // make some adjustments... // try again db.SubmitChanges(); }

24. © Satyam Computer Services Ltd. 2008 LINQ Query to SQL Translation 24 Confidential – Limited Circulation  LINQ to SQL translates the queries you wrote into equivalent SQL queries and sends them to the server for processing.  Because execution is deferred, LINQ to SQL is able to examine your entire query even if assembled from multiple parts.  Queries are not transmitted to the server as IL They are in fact transmitted as parameterized SQL queries in text form. Example: var q = from c in db.Contact where c.DateOfBirth.AddYears(35) > DateTime.Now orderby c.DateOfBirth descending select c; Translates to SELECT [t0].[ContactId], [t0].[FirstName], [t0].[LastName],[t0].[DateOfBirth],[t0].[Phone] FROM [Contact] AS [t0] WHERE DATEADD(YEAR, @p0, [t0].[DateOfBirth]) > @p1 ORDER BY [t0].[DateOfBirth] DESC

25. © Satyam Computer Services Ltd. 2008 Transactions 25 Confidential – Limited Circulation  A transaction is a service provided by databases or any other resource manager that can be used to guarantee that a series of individual actions occur automatically; meaning either they all succeed or they all don't.  If no transaction is already in scope, the DataContext will automatically start a database transaction to guard updates when you call SubmitChanges(). Product prod = q.Single(p => p.ProductId == 15); if (prod.UnitsInStock > 0) prod.UnitsInStock--; db.Transaction = db.Connection.BeginTransaction(); try { db.SubmitChanges(); db.Transaction.Commit(); } catch { db.Transaction.Rollback(); throw; } finally { db.Transaction = null; }

26. © Satyam Computer Services Ltd. 2008 Demo 26 Confidential – Limited Circulation 

27. © Satyam Computer Services Ltd. 2008 27 Confidential – Limited Circulation Exception Handling Application Block

28. © Satyam Computer Services Ltd. 2008 What is Exception Handling Application Block? 28 Confidential – Limited Circulation  It is a part of Patterns & Practices Enterprise Library. Patterns & Practices Enterprise Library is a collection of Application Blocks. Application Blocks are provided in the form of source code as a guidance which can be used as it is, can be extended or can be modified as per the requirements.  It allows developers and policy makers to create a consistent strategy for handling exceptions in the application.

29. © Satyam Computer Services Ltd. 2008 What It Offers? 29 Confidential – Limited Circulation  It allows administrators and policy makers to create policies to handle exceptions. They can maintain and modify policies without changing application code.  It supports exception handling in all layers of an application  It provides common tasks which are required at the time of exception handling. Like logging exception information, replacing original exception with another exception and wrapping original exception inside another exception.  It allows developers to create their own exceptions.

30. © Satyam Computer Services Ltd. 2008 Enterprise Library Installation Information 30 Confidential – Limited Circulation  Latest version : Enterprise Library 3.1 – May 2007  Download Size : 22.9 MB  Link to download : http://www.microsoft.com/downloads/details.aspx?FamilyId=4C557C63- 708F-4280-8F0C-637481C31718&displaylang=en http://www.microsoft.com/downloads/details.aspx?FamilyId=4C557C63- 708F-4280-8F0C-637481C31718&displaylang=en  System Requirements :  Operating Systems: Windows Server 2003, Windows Vista, Windows XP  Microsoft Framework 2.0 or 3.0  Microsoft Visual Studio 2005

31. © Satyam Computer Services Ltd. 2008 Hierarchy of Objects 31 Confidential – Limited Circulation  Configuration  Policies  Exception Types  Exception Handlers  Logging Handler  Wrap Handler  Replace Handler  Custom Handler  Fault Contract Exception Handler

32. © Satyam Computer Services Ltd. 2008 Configuration 32 Confidential – Limited Circulation  It is a configuration file of the application which is created to define policies for exception handling by policy makers. This can be maintained with the help of Enterprise Library Configuration tool. One can also modify the configuration file manually.

33. © Satyam Computer Services Ltd. 2008 Policy 33 Confidential – Limited Circulation  Policy is a collection of one or more exception types with a given name. In your policy you include one or more type of exceptions to handle.  Only specified exceptions can be handled by the policy and not others. But if you pass the inherited exception types then they are handled. If you pass other exception types to the policy then they will not be handled and same exception will be returned.

34. © Satyam Computer Services Ltd. 2008 Exception Types 34 Confidential – Limited Circulation  It is a list of Exception Types to be handled by a policy.  You can specify Post Handling Action for each exception. Possible values are:  None: You don’t want to take any action when this type of exception occurs. Normally you can take this action with Logging Handler. You log the exception and do nothing.  NotifyRethrow: You want to throw the same exception back to the application. Normally you can take this action with Logging Handler. You log the exception and throw back the same exception. Calling method/component can take further action on the exception.  ThrowNewException: You want to throw a new exception to the application. Normally you can take this action with Wrap or Replace Handler. You wrap or replace original exception and throw a new exception.

35. © Satyam Computer Services Ltd. 2008 Exception Handlers 35 Confidential – Limited Circulation  Logging Handler:  Logging exception information is a frequently required task as a part of exception handling.  With the help of this handler we can log the exception information in locations specified in the configuration file.  To use Logging Handler, Logging Application Block must be included in the application.  Logging Handler passes the information to the Logging Application Block to log the exception information.

36. © Satyam Computer Services Ltd. 2008 Exception Handlers 36 Confidential – Limited Circulation  Replace Handler:  You may want to replace the original exception, which contains sensitive or unnecessary information, with another more appropriate exception. For example original exception may contain any URL, any database information etc.  New specified exception will be thrown in place of the original exception.  New exception can have a customized message.

37. © Satyam Computer Services Ltd. 2008 Exception Handlers 37 Confidential – Limited Circulation  Wrap Handler:  You may want to wrap the original exception inside another exception. Wrapping will throw a new exception of the specified type and sets the original exception as InnerException.  Use wrapping in situations where the calling method/component can take decisions on the basis of new exception type. And if required it can use the underlying original exception as well.

38. © Satyam Computer Services Ltd. 2008 Exception Handlers 38 Confidential – Limited Circulation  Custom Handler:  You may want to throw your own customized exception type in place of original exception. For that create an exception class which implements IExceptionHandler and use it in the Custom Handler.

39. © Satyam Computer Services Ltd. 2008 How It Works 39 Confidential – Limited Circulation  Add the reference of necessary Exception Handling Application Block DLLs from Enterprise Library into the application. If you are using Logging Handlers then also take the reference of necessary Logging Application Block DLLs.  Create a config file & Define policies into the config file

40. © Satyam Computer Services Ltd. 2008 How It Works 40 Confidential – Limited Circulation

41. © Satyam Computer Services Ltd. 2008 How It Works 41 Confidential – Limited Circulation  Deploy the configuration file at all layers of the application where you want to have Exception Handling functionality.  Call the policy to handle the exception where you want to use the policy. You call the policy into the Catch block and pass the exception to the policy. Policy will execute all handlers one by one assigned for the passed the exception.

42. © Satyam Computer Services Ltd. 2008 How It Works 42 Confidential – Limited Circulation Imports Microsoft.Practices.EnterpriseLibrary.ExceptionHandling Public Class clsDAL Public Function GetData() As DataSet Dim DS As New DataSet Try ' Data access code will come here. Catch ex As Exception Call HandleExceptions(ex) End Try Return DS End Function Private Sub HandleExceptions(ByVal Ex As Exception) Dim showErr As Boolean Dim HandlerEx As New Exception showErr = ExceptionPolicy.HandleException(Ex, "DALPolicy", HandlerEx) If Not HandlerEx Is Nothing Then Throw HandlerEx Else If showErr = True Then Throw Ex End If End Sub End Class

43. © Satyam Computer Services Ltd. 2008 Multi-tier architecture View 43 Confidential – Limited Circulation

44. © Satyam Computer Services Ltd. 2008 Multi-tier architecture View 44 Confidential – Limited Circulation  Exceptions that occur in the data access layer are logged and then wrapped inside another exception that provides more meaningful information to the calling layer. Within the business component layer, the exceptions are logged before they are propagated.  Any exceptions that occur in the business component layer and that contain sensitive information are replaced with exceptions that no longer contain this information. These are sent to the user interface (UI) layer and displayed to the user.

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