November, 2007

I started playing with Lambda expression after the TechEd demo by Anders Hejlsberg. Couple of nice things I would like to share with you.

As there might be many definitions for Lambda expression but to me Lambda Expression is the concise way to write functional implementation for Anonymous Method. This is been used by compiler to translate LINQ to method calls. This also allows us to maintain 100% backward compatibility with any managed version of C#.

Lambda function can be created using the Generic delegate Func. Func<A,R> (represents a function taking an argument of type A and returning a value of type R) is the predefined .NET call to a delegate for n number of parameters with any type. Life is easy for us. Func is defined inside System.Linq namespace. So being developer we do not have to bother about the number of variable and there types. We can simply go ahead and create any function using Func.

Now if you have an anonymous method for a List of Integers which finds the even numbers from the list.

//Generic List of Integers

List<int> arrInt = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

//Using delegate (anonymous method) get the even numbers

List<int> even1 = arrInt.FindAll(delegate(int i2) { return i2 % 2 == 0; });

//dump them in the console

foreach (int j in even1)

{

    Console.WriteLine(j);

}

Now, if I want to implement Lambda Expression there the code will look like,

//Generic List of Integers

List<int> arrInt = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

//Using Lambda Expression get the even numbers

List<int> even1 = arrInt.FindAll(i => i % 2 ==0);

//dump them in the console

foreach (int j in even1)

{

    Console.WriteLine(j);

}

Now, if you want to create the same list by using Lambda Expression and Func

//This means I am creating a function which

//takes an argument integer and returns bool.

Func<int, bool> EvenGetter = x => x % 2 == 0;

//Generic List of Integers

List<int> arrInt = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

//Using Lambda Expression get the even numbers

IEnumerable<int> even1 = arrInt.Where(EvenGetter);

//dump them in the console

foreach (int j in even1)

{

    Console.WriteLine(j);

}

So here we are reusing a Function with the name EvenGetter and this is like any other function not in embedded.

Func is very powerful, we can create List of Lambda Expression Functions and iterate through the list and check one input through multiple functions,

Let us assume that I need to pass one integer and get some four out puts. I will create Generic List of Func’s which takes one argument as double and returns double.

List<Func<double, double>> funcs = new List<Func<double,double>>();

//Add function to the list

funcs.Add(x => x * x); //Get the square

funcs.Add(x => 1 / x);

funcs.Add(x => Math.Sqrt(x)); //Sqr root of x

//iterate through the list

foreach (var f in funcs)

{

    //Execute the functions one by one with the value 100

    Console.WriteLine(f(100));   

}

Output

---------

10000

0.01

10

Press any key to continue . . .

 This is pure functional programming.

Namoskar!!!

Visual Studio 2008 Training Kit videos are now available on web. Get some real exciting presentations

VS2008 Training Kit: What's new in C# 3.0?

VS2008 Training Kit: What's new in Visual Basic 9.0?

VS2008 Training Kit: .NET Language Integrated Query (LINQ)

VS2008 Training Kit: Using LINQ with Relational Data

For more detailed list please visit http://channel9.msdn.com/Showforum.aspx?forumid=38&tagid=267

Enjoy learning.

Namoskar!!!

Some of the early adopters case studies are now available,

Xcalia

OpenNETCF Consulting

Sogeti Group

K2

Get some of the quotes from there,

LINQ is an object-oriented language and so fits perfectly with the philosophy of our product, which aims to make technical details of data access transparent to the developer.

LINQ helped us simplify how we targeted code objects and dictionaries inside our product. Experiencing it firsthand has made us quite enthusiastic about the technology.

We believe that LINQ is more than just a query language for retrieving data from data sources. In fact, it should also be considered as another way to implement your algorithm in your application.

We were looking everywhere for something to help us test our AJAX code, and the features in Visual Studio Team System are some of the best around.

We’ll ship better quality code earlier. Development and support costs will drop dramatically because we can find bugs earlier through better testing.

We now spend less time doing product support and more time producing new code because the applications are more reliable.

I opened up the code in Visual Studio 2008 Professional, and in three to four minutes, I recompiled some 100,000-plus lines of code

The kind of agility we got from Visual Studio Team System 2008 Architecture Edition at both the micro and system level saved lots of time by making modeling easier.

These are from real world implementation.

Namoskar!!!

Get it printed and paste in your cubicle,

Visual C# 2008 Poster

.NET Framework 3.5 Common Namespaces and Types Poster

Other posters are available also at Microsoft Downloads.

Namoskar!!!

As usual Express editions are free but this time you can take this and sit in a remote location and install Visual Studio with no Internet connections. Yes we can download offline .iso to avoid download & install pain.

Please visit, http://www.microsoft.com/express/download/offline.aspx

After downloading you can write them in DVD. This version includes all the Express Editions.

So enjoy with this light-weight Visual Studio 2008 and have the magic. You can also install .iso by creating virtual drive by using utility such as Daemon.

Namoskar!!!

From code name “cool” to C# 3.0, it’s been a long journey for this amazing language with .NET Runtime. Here I am going to show you the evaluation step by step.

Let us assume we have generic list of integers and I need to find the even numbers from that list,

List<int> arrInt = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

C# Way: Beginners

+++++++++++++

List<int> even1 = new List<int>();

foreach (int i in arrInt)

{

    if (i % 2 == 0)

        even1.Add(i);               

}

foreach (int item in even1)

{

    Console.WriteLine(item);

}

C# 1.1 Way: Using Delegate

+++++++++++++++++++

Using Predicate<T> we can call delegate and then with some existing method’s help I can get the data as I require.

So the method I need here will look like,

public static bool EvenGetter(int i2)

{

    return i2 % 2 == 0;

}

Now the predicate implementation seems something like,

List<int> even1 = arrInt.FindAll(new Predicate<int>(EvenGetter));

foreach (int item in even1)

{

    Console.WriteLine(item);

}

C# 2.0 Way: Using Anonymous Method

++++++++++++++++++++++++++

Anonymous Methods helps us to implement delegate without having any method.

List<int> even1 = arrInt.FindAll(delegate(int i2) { return i2 % 2 ==0; });

foreach (int item in even1)

{

    Console.WriteLine(item);

}

C# 3.0 Way: Using Lambda Expression

++++++++++++++++++++++++++

Hmm, this is magic. Please refer C# 3.0 Specification for more information.

List<int> even1 = arrInt.FindAll(i => i % 2 == 0);

foreach (int item in even1)

{

    Console.WriteLine(item);

}

C# 3.0 Way: Implementing LINQ

++++++++++++++++++++++

Write SQL like query as native statement, LINQ Rocks!!!

IEnumerable<int> even1 = from i in arrInt

                         where i % 2 == 0

                         select i;

foreach (int item in even1)

{

    Console.WriteLine(item);

}

This is the actual conversion happens when you compile the above code.

IEnumerable<int> even1 = arrInt.Where(i => i % 2 == 0);

Actual IL (disassembled) generated code looks like,

IEnumerable<int> even1 = <>g__initLocal0.Where<int>(delegate (int i) {

        return (i % 2) == 0;

    });

Pure code.

Namoskar!!!

LINQ to SQL supports hierarchical data and you can easily create a query and get output from there. Let us take an example of Northwind database. Northwind has Category -> Products -> Order_Details tables. -> indicates one to many relationships here. So ideally for a Category can have multiple products and a product can have multiple Orders (in Order_Details). Now to get the number of Orders given for each Products under a category of id with their total price we have to write sub queries and SQL will become complex.

But if we use LINQ to SQL and drag and drop all the three tables there. The designer will look like,

Now to get the required output we can write a simple LINQ statement,

NorthwindDataContext db = new NorthwindDataContext();

var query =

from p in db.Products

where p.CategoryID == 1

select new

{

p.ProductID,

p.ProductName, 

p.Category.CategoryName,

     NumOrders = p.OrderDetails.Count,

     Revenue = p.OrderDetails.Sum(o=>o.UnitPrice * o.Quantity)

};

TextBox1.Text = db.GetCommand(query).CommandText;

Namoskar!!!

LINQ to SQL we can read the generated T_SQL query using DataContext.Log or SQLQueryVisualizer. But If you are working with WebProject the Log property not very much convenient as you have to use TextWriter to dump the generated T-SQL query.

In Orcas Beta 1 we had DataContext.GetQueryText which used to give us the generated T-SQL now we do not have this from Visual Studio 2008 Beta 2. I have mentioned about this change in one of my earlier Blog post. The implementation is here,

TextBox1.Text = db.GetCommand(query).CommandText;

Now this will give you the DataContext generated T-SQL query.

ADO.NET 2.0 offers us a unique feature through which we can make a real lightweight DataSet. This is very important and much neglected development practice to overlook the performance part. So when you have huge data and you are getting multiple hit this small tune may help you a lot.

Assume I am working with Orders table and creating a DataSet out of it. Now this DataSet can be shared through network. When we pass the data the bigger stream size can create problem. Let us create a text file to check the size,

DataSet dsOrders = new DataSet();

using (SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Orders", CONN_STR))

{

    da.Fill(dsOrders);

    gridOrders.DataSource = dsOrders;

    gridOrders.DataMember = dsOrders.Tables[0].TableName;

}

//Setting the Property to make it lightweight

dsOrders.RemotingFormat = SerializationFormat.Binary;

BinaryFormatter bf = new BinaryFormatter();

using (FileStream fs = new FileStream(@"C:\DataSet_2.txt", FileMode.OpenOrCreate))

{

    bf.Serialize(fs, dsOrders);

}

If you do not set the SerializationFormat.Binary then the default setting is SerializationFormat.Xml. This is huge compared to Binary.

Size of the generated file, is

Xml     :  434 KB

Binary :  139 KB

Namoskar!!!

You all probably know what is “var”. You might have a question why this new keyword is required in programming language like C#. One of the few strong reasons is to have an Anonymous Type stored in a variable. Whenever you have to initialize a type you have to mention the type before you give a name for a variable. But can you do something like this,

AnonymousType~1 obj = new {Id = 1, Name="Wriju"};

The anonymous type will be decided during compile time and it is random. You simple cannot assume anything here.  The proper way of declaration would be,

var obj = new {Id = 1, Name="Wriju"};

Another area in LINQ where to get multi column output we often use anonymous type and get the IEnumerable of that type. So when you have no type in place can you declare IEnumerable of that type?

var q = from c in db.Customers

        select new { c.CompanyName, c.ContactName };

If you want to have IEnumerable<T> then you have to have type T defined in your apps somewhere. But it is very inconvenient to have a type defined every time you want to get a different combination.

Things to remember,

Ø       var cannot be used as public property/field

Ø       var cannot be a return type of any method

Otherwise var rocks and it is Reflection enabled. Performance is equal.

Namoskar!!!

LINQ to SQL designer in Visual Studio allows us to create mapped class using the drag and drop feature from Server Explorer. Now that is business object which ideally you could use as your datasource and from Visual Studio 2008. So let us have this step by step,

Open your Visual Studio 2008 and create a new Windows Forms application (assume C#).

Now add new item to the project LINQ to SQL (.dbml). Give name NW.dbml.

Open a new Data Connection from your VS 2008’s Server Explorer window.

Point to Northwind database. Drag and drop Customers and Orders table. Since Customer and Order table has one to many relationship the designer will get generated like below,

Now open a data source from Data menu of your VS 2008. Click on add new Datasource. Add object DataSource.

Now click on next, choose Customer.

Click next and finish.

Now your datasource window will show both Customer and Order because they are connected through PK/FK.

Make Customer as details view

Drag Customer to your Windows Forms. Then all the navigator and grid will be created as the RAD (Rapid Application Development).

Now you also drag and drop Orders (this will create DataGrid). Now a add the code to your form_load event.

Final look,

Namoskar!!!

Some of the best blogs on LINQ to SQL I found are available for great learning,

Scott Guthrie

The Famous LINQ TO SQL Series

• Part 1: Using LINQ to SQL
• Part 2: Defining our Data Model Classes
• Part 3: Querying our Database
• Part 4: Updating our Database
• Part 5: Binding UI using the ASP LinqDataSource Control
• Part 6: Retrieving Data Using Stored Procedures
• Part 7: Updating our Database using Stored Procedures
• Part 8: Executing Custom SQL Expressions

There are several good new blogs from members of the Microsoft C# team. Nevertheless, the most important items in this edition of Community Convergence are Rico Mariani's series of articles on LINQ to SQL performance.

• LINQ to SQL Performance Part 1
• LINQ to SQL Performance Part 2
• LINQ to SQL Performance Part 3
• LINQ to SQL Performance Part 4
• LINQ to SQL Performance Part 5

Namoskar!!!