1. Sarang S. Datye Microsoft Global Services India
Enhancing Developer Productivity -
The LINQ way.
Sarang S. Datye
Microsoft Global Services India

2. Agenda Introduction Comparing ADO.NET with LINQ DataContext
Understanding DataContext against IDbConnection
Attribute Mapping
Mapping .NET Objects to SQL Object
CodeGen tools
VS Designer, SQLMetal
DML thru LINQ to SQL
Using LINQ to perform Insert, Update, Delete
Using Stored Procedures
Calling Stored Procedures to bind with .NET Objects
LINQ Transactions
Enlisting LINQ queries in transactions

3. Introduction LINQ = Language INtegrated Queries
Query Expression, Lambdas, Extension methods…
LINQ to SQL = Managing Relations data as objects using LINQ

4. LINQ to SQL Accessing data today
Queries in quotes
SqlConnection c = new SqlConnection(…);
c.Open();
SqlCommand cmd = new SqlCommand(
@"SELECT c.Name, c.Phone
FROM Customers c
WHERE c.City
"London“);
DataReader dr = c.Execute(cmd);
while (dr.Read()) {
string name = dr.GetString(0);
string phone = dr.GetString(1);
DateTime date = dr.GetDateTime(2); }
dr.Close();
Loosely bound arguments
Loosely typed result sets
No compile time checks

5. LINQ to SQL Accessing data with LINQ
Classes describe data
public class Customer { … }
public class Northwind : DataContext {
public Table<Customer> Customers; … }
Tables are like collections
Strongly typed connections
Northwind db = new Northwind(…);
var contacts =
from c in db.Customers
where c.City == "London"
select new { c.Name, c.Phone };
Integrated query syntax
Strongly typed results

6. LINQ to SQL Language integrated data access Mapping Persistence
Maps tables and rows to classes and objects
Builds on ADO.NET and .NET Transactions
Mapping
Encoded in attributes or external XML file
Relationships map to properties
Persistence
Automatic change tracking
Updates through SQL or stored procedures

7. DataContext
A DataContext is used to scope changes made to classes defined by LINQ to SQL
A DataContext is responsible for keeping references to all LINQ to SQL classes, their properties, and foreign key relationships.
A DataContext is not meant to be kept around; we want to create a new context for every “unit of work” to avoid concurrency issues. There are multiple ways to approach this.
A DataContext is the API to the database, but at this stage it does not contain any business logic that is not implied by the database schema.

8. DataContext
NorthwindDataContext context = new NorthwindDataContext("server=.; database=northwind; integrated security=true");

9. Defining DataContext Inherit from DataContext Override Constructor(s)
[Database(Name = “MyDB")]
public class MyDataContext : DataContext {
public MyDataContext(string connString)
: base(connString) }

10. Creating DataContext Similar to SqlConnection()
public static void Main() {
string connString = “server=MyServer; database=MyDb”;
MyDataContext context = new MyDataContext(connString); : }

11. DataContext Demo

12. LINQ Queries SQL “like” Syntax Not a hack/kludge Built upon Generics
Extension methods
Lamdas
var result = from cust in context.Customers
where cust.Location = “Pune”
select cust;
foreach (Customer c in result) {
Console.WriteLine(c.CustomerName); }

13. LINQ Queries LINQ To SQL fetches data from database
Populates the Table Object/EntitySet
Basic LINQ semantics allows iteration

14. join Query SQL “Like” join Inner join implemented as natural syntax
Outer joins thru “DataShapes”
var result = from c in Customers
join o in Order on c.CustomerID equals o.CustomerID
select new { c.CustomerName, o.OrderID }
foreach (var v in result) {
Console.WriteLine(v); }

15. Outer Joins Use DataShape to associate
DataShape shape = new DataShape();
shape.LoadWith<Person>(p => p.Address);
Context.Shape=shape;

16. JOIN DEMO

17. Inner Joins
SELECT [t1].[ASListID], [t1].[QID]
FROM [Question] AS [t0]
INNER JOIN [QuestionSelection]
AS [t1] ON [t0].[QID] = [t1].[QID]
WHERE EXISTS( SELECT t3.ASListID
FROM [AnswerStep] AS [t2]
INNER JOIN [AnswerStepSelection] AS [t3] ON [t2].[ASID] = [t3].[ASID]
INNER JOIN [AnswerStepList] AS [t4] ON [t3].[ASListID] = [t4].[ASListID]
WHERE ([t3].[ASListID] = [t1].[ASListID]) AND ([t4].[QuestionAreaID] = 1) )
(from t in context.GetTable<ConsoleApplication3.TailoringQuestion>()
join t1 in context.GetTable<ConsoleApplication3.TailoringQuestionSelection>()
on t.TQID equals t1.TQID
select new { t1.PSListID, t1.TQID }).Where(n => (from p in context.GetTable<ConsoleApplication3.ProgramStep>()
join p1 in context.GetTable<ConsoleApplication3.ProgramStepSelection>()
on p.PSID equals p1.PSID
join p2 in context.GetTable<ConsoleApplication3.ProgramStepList>()
on p1.PSListID equals p2.PSListID
where ((p2.AuditAreaID == 1))
select p1.PSListID).Contains(n.PSListID));

18. Attribute Mapping Declarative mapping No code required
Map Relational to Objects
[Table(Name=“prod”)]
public class Product {
[Column(Name=“ProdId”, IsPrimaryKey=true)]
public string ProductID;
[Column]
public string ProductName; }

19. Attribute Mapping Demo

20. XML Mapping Externalized mapping Can be modified without rebuild
Can be generated dynamically

21. Sample xml mapping file
<?xml version="1.0" encoding="utf-8"?>
<Database Name="northwind" xmlns="
<Table Name="dbo.Customers" Member="Customers">
<Type Name="Customer">
<Column Name="CustomerID"
Member="CustomerID"
Storage="_CustomerID"
DbType="NChar(5) NOT NULL"
CanBeNull="false"
IsPrimaryKey="true" />
<Column Name="CompanyName"
Member="CompanyName"
Storage="_CompanyName"
DbType="NVarChar(40) NOT NULL"
CanBeNull="false" />
</Type>
</Table>
</Database>

22. XML Mapping Demo

23. Code Generation Tools Attribute and XML can be manually generated
CodeGen Tools
VS Designer Tool
Link to SQL class item
Server Explorer Drag and Drop
SQLMetal.exe
Can generate DBML (Database Markup Language)
XML Mapping File
Attribute mapped code file (.cs|.vb)
VLinq
Visual design LINQ Queries

24. SQLMetal Demo

25. LINQ Associations Mirror database relation in object collection
Master-Detail mapping
Data available thru Object Collections
[Table(Name=“Customers”]
Class Customer {
[Column] public string CustomerID;
[Column]public string CompanyName;
[Association(ThisKey=“CustomerID”, OtherKey=“CustomerID”]
public EntitySet<Order> orders; }
[Table(Name=“Orders”)]
public class Order
[Column] public stringOrderID;

26. Association Thru XMLMapping
Similar to attribute
<?xml version="1.0" encoding="utf-8"?>
<Database Name="northwind" xmlns="
<Table Name="dbo.Customers" Member="Customers">
<Type Name="Customers">
<Column Name="CustomerID" Member="CustomerID" Storage="_CustomerID" DbType="NChar(5) NOT NULL" CanBeNull="false" IsPrimaryKey="true" />
<Column Name="CompanyName" Member="CompanyName" Storage="_CompanyName" DbType="NVarChar(40) NOT NULL" CanBeNull="false" />
<Association Name="FK_Orders_Customers" Member="Orders" Storage="_Orders" ThisKey="CustomerID" OtherKey="CustomerID"/>
</Type>
</Table>
<Table Name="dbo.Orders" Member="Orders">
<Type Name="Orders">
<Column Name="OrderID" Member="OrderID" Storage="_OrderID" DbType="Int NOT NULL IDENTITY" IsPrimaryKey="true" IsDbGenerated="true" AutoSync="OnInsert" />
<Column Name="CustomerID" Member="CustomerID" Storage="_CustomerID" DbType="NChar(5)" />
<Column Name="OrderDate" Member="OrderDate" Storage="_OrderDate" DbType="DateTime" />
</Database>

27. Association Demo

28. Call StoreProcedures SPs can be mapped thru attributes or XML
Call semantics similar to tables
Supports parameter passing (in/out)
Existing Entity behaviour can be changed to use SPs instead of SQL

29. LINQ to Entities using(AdventureWorksDB aw = new
AdventureWorksDB(Settings.Default.AdventureWorks)) {
Query<SalesPerson> newSalesPeople = aw.GetQuery<SalesPerson>(
"SELECT VALUE sp " +
"FROM AdventureWorks.AdventureWorksDB.SalesPeople AS sp " +
"WHERE sp.HireDate
new hireDate));
foreach(SalesPerson p in newSalesPeople) {
Console.WriteLine("{0}\t{1}", p.FirstName, p.LastName); }
using(AdventureWorksDB aw = new
AdventureWorksDB(Settings.Default.AdventureWorks)) {
var newSalesPeople = from p in aw.SalesPeople
where p.HireDate > hireDate
select p;
foreach(SalesPerson p in newSalesPeople) {
Console.WriteLine("{0}\t{1}", p.FirstName, p.LastName); }

30. LINQ to Entities..contd. LINQ to SQL ADO.NET Entities Framework
Database Support
SQL Server
Many
Object Relational Mapping Capabilities
Simple -> 1:1
Complex
Metadata
Attributes
edmx file

31. LINQ to DataSets Accessing from the DataSet with Joins
DataSet ds = new DataSet();
FillOrders(ds);
DataTable orders = ds.Tables["SalesOrderHeader"];
DataTable details = ds.Tables["SalesOrderDetail"];
var query = from o in orders.ToQueryable()
join d in details.ToQueryable()
on o.Field<int>("SalesOrderID") equals
d.Field<int>("SalesOrderID")
where o.Field<bool>("OnlineOrderFlag") == true
select new { SalesOrderID = o.Field<int>("SalesOrderID"),
OrderDate = o.Field<DateTime>("OrderDate"),
ProductID = d.Field<int>("ProductID"),
Quantity = d.Field<short>("OrderQty") };
foreach(var line in query) {
Console.WriteLine("{0}\t{1:d}\t{2}\t{3}",
line.SalesOrderID, line.OrderDate,
line.ProductID, line.Quantity); }
Accessing from the DataSet
DataSet ds = new DataSet();
FillOrders(ds); // this method fills the DataSet from a database
DataTable orders = ds.Tables["SalesOrderHeader"];
var query = from o in orders.ToQueryable()
where o.Field<bool>("OnlineOrderFlag") == true
select new { SalesOrderID = o.Field<int>("SalesOrderID"),
OrderDate = o.Field<DateTime>("OrderDate") };
foreach(var order in query) {
Console.WriteLine("{0}\t{1:d}", order.SalesOrderID, order.OrderDate); }

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