leveraging c# 3.0 and linq-mm

8/8/2019 Leveraging C# 3.0 and LINQ-MM

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Leveraging C# 3.0 &

LINQKrishnan Subramanian


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Agenda

Architectures

Layers

Data access Business logic

Service logic

UI

Wrap up


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Architectures


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LINQ to SQLApplication

SQL Server

LINQ to SQL

from c in db.Customers

where c.City == "London"

select c.CompanyName

LINQ Query

SQL Query

SELECT CompanyName

FROM dbo.Customers

WHERE City = 'London'

Rows

ObjectsSubmitChanges()

DML or SProcs

db.Customers.InsertOnSubmit(c1);

c2.City = "Seattle";

db.Customers.DeleteOnSubmit(c3);

INSERT INTO Cust

UPDATE Cust

DELETE FROM Cust


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Data access layer

What defines a data access layer?

Or, how do you recognize a class belongs to a data access

layer?

LINQ to SQL / LINQ to entities

Is it a DAL?

Do not confuse Language Integrated Queries (LINQ) with

SQL


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LINQ to SQL: validation

LINQ to SQL is all generated code

Domain entities + relationships

Simple validation vs complex validation


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LINQ to SQL: simple validation


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LINQ to SQL: validation

Simple validation:

Dos:

Leverage partial classes Leverage partial methods

Donts:

Directly modify generated code


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LINQ to SQL: advanced mapping

M : N relationships

Should be easy to navigate (read) M : N relationships

Custom aggregations/associations E.g. customer has an 'Address' property


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Advanced mapping:

Dos:

Leverage partial classes (again!)


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LINQ to SQL: data shaping

Querying in the object world! = SQL

LINQ (to SQL) is not constrained like SQL

Can manufacture hierarchies & arbitrary nestings

Can manufacture relationships not in the domain model


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Data shaping

Dos:

Think about querying the domain model and not SQL Leverage C# 3.0s anonymous types & object initializers

Leverage LoadWith and AssociateWith methods on

DataLoadOptions class


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LINQ to SQL: query composability

Leverage deferred query execution


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Query composability


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LINQ to SQL: query composability

Query composability

Dos:

Return types are IQueryable and notIEnumerable

Judicious use; can be abused!

DataContext DOs apply

Donts:

Create N methods forN query variants


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LINQ to SQL: paging


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LINQ to SQL: paging


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LINQ to SQL: paging

Paging

Dos:

Paging is built-in! Super simple! Works with SQL Server 2000, 2005, 2008 (VS 2008

SP1)

Donts:

Re-invent the wheel


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LINQ to SQL: dynamic queries

I dont know what the 'where'-clause looks like!


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Dynamic queries

Dos:

U

nderstand expression trees Build expression trees:

Dynamically (can be complex)

From stringified values (simple, but not type safe)


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Service logic


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Service logic

WS - *

Explicit contracts (document centric)

Data on the outside! = data on the inside Translation required

Data services

REST/POX based


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Service logic


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Service logic: WS - *

WS - * based:

Dos:

Leverage object initializers Easy to write

Code readability and maintainability increase

Use extension methods for translations

Queries & chaining of extension methods


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Clients


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Clients


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Summary

Explicit data access layer almost disappears

Rest of the layers 'slimmed' down

LINQ + C# 3.0 features results in code that:

Is readable

Is maintainable

Specifies intent vs being imperative (just makes it work )


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Join the 2-day LINQ masterclass

www.microsoft.nl Training & Events MSDN

Or drop me an email: [email protected]

Microsoft Services


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leveraging c# 3.0 and linq-mm

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