What are Immutable types?

In C#, primarly we have two types of objects: reference type and value type. Value type objects always have default value and created on stack. When we assign value type variable to another variable, a new copy gets created. While reference type objects default to null and created on heap. Multiple variables can point to the same object, it means changing the value using one, will reflect accross variables. There is one more type called Nullable type which is similar to value type with additional capability to have no value if it is unassigned. You can learn more about from one of my previous posts here

A reference type can be categorized in two types : Mutable and Immutable. The plain english meaning is “Can Change” and “Cannot Change” respectively and which is same here as well.

It means an Immutable type object cannot be changed after it’s creation/initialization and if one tries to change, a new copy gets created (if allowed) and returned. In other words, it is a reference type but having value type semantics. String is one of the most used immutable types and it is provided by the .NET framework.

Normal class that we create, are mutable type. Let’s see an example

    class Program
    {
        static void Main(string[] args)
        {
            Person objPerson = new Person() { Name = "Brij", Age =32 };
            UpdatePerson(objPerson);
            Console.WriteLine(objPerson.Name);
            Console.ReadKey();
        }

        static void UpdatePerson(Person P)
        {
            P.Name += " Mishra";
        }
    }

    public class Person
    {
        public string Name { get; set; }

        public int Age { get; set; }
    }

So in this example the output will be Brij Mishra as the same object got changed. This class can also be modified as where we just provide the getter and the values then can be modified either at constructor or any other method inside the same class.

public class Person
{
    private string _name;
    public string Name { get { return _name; } }

    private int _age;
    public int Age { get { return _age; } }

    public Person(string name, int age)
    {
        this._name = name;
        this._age = age;
    }
}

Now to make it an immutable object, we have two options:

  1. Use Const
  2. Use Readonly

So I can make the class as

   public class Person
    {
        private readonly string _name;
        public string Name { get { return _name; } }

        private readonly int _age;
        public int Age { get { return _age; }  }

        public Person(string name, int age)
        {
            this._name = name;
            this._age = age;
        }
    }

Now once we create an instance of this class, it cannot be updated as all the properties are readonly. Even, we cannot update in another new method in the same class as in the previous example. We can use the Const instead of readonly but in that case, we will loose the ability to assign the value while object creation, instead we will have to provide the value at class definition. One more drawback, as const variable initialized at Class level itself, also called compile time constant so it would be same for all the instances of that type.

Now lets create another class address and have a List of Addresses in the class as

 public class Person
    {
        private List
<Address> _addresses;
        private readonly string _name;
        public string Name { get { return _name; } }

        private readonly int _age;
        public int Age { get { return _age; }  }

        public Person(string name, int age, List
<Address> addresses)
        {
            this._name = name;
            this._age = age;
            _addresses = addresses;
        }
        public List
<Address> Addresses { get { return _addresses; } }
    }

    public class Address
    {
        public string Address1 { get; set; }

        public string Address2 { get; set; }

        public string City { get; set; }

        public string State { get; set; }

        public string Zip { get; set; }
    }

As here the list of address has only get property exposed, it means we cannot replace the whole collection but certainly we can update the items from the list by adding and/or removing an item as

Person objPerson = new Person("Brij", 32, addresses);
objPerson.Addresses.Add(new Address());

Now, to make the Person class Immuatble, we need to change it as readonly collection as

public class Person
{
    private List
<Address> _addresses;
    private readonly string _name;
    public string Name { get { return _name; } }

    private readonly int _age;
    public int Age { get { return _age; }  }

    public Person(string name, int age, List
<Address> addresses)
    {
        this._name = name;
        this._age = age;
        _addresses = addresses;
    }

    public ReadOnlyCollection
<Address> Addresses { get { return _addresses.AsReadOnly(); } }
}

Now we wont be able to add or remove items from list. Still we have here one gap and using we can update any existing address object as Address is not a immutable type.

To make it immutable we will require to make all the properties readonly or const.

So to make an object immuatble, all the internal type used, should also be immutable and all the collection should be readonly.

C# 6 added a feature that says if we have a auto property with only a getter then it can be only initialized in constructor. Behaind the scene, it uses private readonly property as

public class Person
{
    public string Name { get; }

    public int Age { get; }
}

Here if we try to update the properties other than the constructor, it will throw an error stating that it is readonly.

Hope you all have enjoyed the post.

Cheers
Brij

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TransactionScope: A simple way to handle transactions in .NET

Have you ever tried implementing transactions using C# code? Normally, we implement transactions in SQL where multiple Insert/Update statements takes part in it. A Transaction follows the ACID (Atomicity, Consistency, Isolation, Durability) rule where either all the statements get committed or all get canceled and rolled back. TransactionScope allows us to implement it at application level. There could be some scenarios where you are required to do different operations in the same database or even multiple databases (distributed transaction) or due to some other constraints, it cannot be done at database level. It is also very helpful for application developers if they have less exposure to database.

What is TransactionScope

TransactionScope got introduced with .NET 2.0 as part of  System.Transaction. It is a class which provides a simple way to make a set of operations as part of a transaction without worrying about the complexity behind the scene. If any of the operation fails in between, entire transaction would fail and rolled back  which undo all the operation that got completed. All this would be taken care by the framework, ensuring the data consistency.

How to use the TransactionScope?

To use this, you need to add the reference of System.Transactions reference which is part of framework libraries (normally it wont be added by default). Once it get added, add the namespace System.Transactions wherever we want to use this. The syntax would look as

try
{
    using (TransactionScope scope = new TransactionScope())
    {
        // Do Operation 1
        // Do Operation 2
        //...

        // if all the coperations complete successfully, this would be called and commit the trabsaction. 
        // In case of an exception, it wont be called and transaction is rolled back
        scope.Complete();
    }
}
catch (ThreadAbortException ex)
{
    // Handle exception
}

Here we can see that we have used Disposable block while creating instance of TransactionScope, it makes sure the dispose gets called when it gets out of the block and ends the transaction scope.

In one Transaction scope, we can do multiple operation connecting to different databases as

using (TransactionScope scope = new TransactionScope())
{
    using (con = new SqlConnection(conString1))
    {
        con.Open();

        // Do Operation 1
        // Do Operation 2
        //...
    }

    using (con = new SqlConnection(conString2))
    {
        con.Open();

        // Do Operation 1
        // Do Operation 2
        //...

    }

    scope.Complete();
}

Here we are using two connection strings to connection different databases. We can use as many based on our requirement. We can have nested transactions as well. It could be as

public void DoMultipleTransaction()
{       
    try
    {
        using (TransactionScope scope = new TransactionScope())
        {
            using (con = new SqlConnection(conString1))
            {
                con.Open();
                // Do Operation 1
            }

            OtherTransaction();
            scope.Complete();
        }
    }
    catch (ThreadAbortException ex)
    {
        // Handle exception
    }
}

private void OtherTransaction()
{
    using (TransactionScope scope = new TransactionScope())
    {
        using (con = new SqlConnection(conString2))
        {
            con.Open();
            // Do Operations
        }
        scope.Complete();
    }
}

Here the outermost transaction is called as rootscope and here even if the inner transaction (OtherTransaction above) gets completed by calling scope.Complete(), if the rootscope complete could not be called due to various reasons, then the complete transaction would be rolled back including inner transactions.

Note: You might get one of the following exception while executing distributed trsanctions

  1. MSDTC on server is unavailable
  2. Network access for Distributed Transaction Manager (MSDTC) has been disabled.

 

Both the error are due to the same reason, first one occurs when you have the database and the application the same server while 2 if on the other server. For same server, go to run-> cmd-> services.msc. Run the service named Distributed Transaction Coordinator and make the startup type automatic so that it gets started again in case of system restart. For 2, follow the link to cofigure MSDTC.

TransactionScope provides various TransactionScopeOptions which defines transactions behavior for the scope. Lets see an example

using (TransactionScope scope = new TransactionScope())
{
    // Do Operation
    using (TransactionScope scope1 = new TransactionScope(TransactionScopeOption.Required))
    {
        // Do Operation
        scope1.Complete();
    }
    using (TransactionScope scope2 = new TransactionScope(TransactionScopeOption.RequiresNew))
    {
        // Do Operation
        scope2.Complete();
    }
    using (TransactionScope scope3 = new TransactionScope(TransactionScopeOption.Suppress))
    {
        // Do Operation
        scope3.Complete();
    }

    scope.Complete();
}

Here we created three transactions under the parent transaction with different TransactionScopeOptions. By default the scope is required, which applies to parent transaction here. It is a rootscope which creates a new transaction, and mark it as an ambient transaction. scope1 is also created with required and as we have already an ambient transaction (scope) so it joins the parent transaction. scope2 got created with option as RequiresNew which means it is a new transaction which is independently works with ambient transaction. scope3 got created with suppress option, which means it doesn’t take part in any ambient transactions. It gets executed regardless whether ambient transaction executes successfully or not. All the ambient transactions gets committed once the parent (global) scope completes.

Hope you enjoyed this post and will be using transaction in your future requirements.

Cheers,
Brij

TracePoint : An awsome feature of Visual Studio

Have you ever wanted to see the intermediate values of a variable which is inside a loop without pausing the execution via breakpoint?

I am sure you will say YES. A visual studio feature called Tracepoint can be very helpful in these scenarios.

Breakpoint allows to stop at a point where you can see the variable value but you may loose the track of it loops for more than 4-5 times.

Tracepoint is an awesome feature of Visual Studio and it is available since Visual Studio 2005. It allows you to write the values in output window without even stopping at any point or you can stop it after the loop and see how the loop progressed based on your needs. I recently started using it and found is very useful. I am sure it is relatively less used.

Let’s see an example. Here I have created a simple program which finds out the nth number in a fibonacci series. Lets see the code

Now I am going to set a tracepoint at line #41. To set up a tracepoint, one need to set up a breakpoint and right click on it which provides few options, then select Actions which opens window as

(In earlier versions of Visual Studio, the options was named as Choice which is Actions as mentioned above)

Here I have written i={i} => result={result} . The values insde {} are the variable names in the program and the value of these variables will be printed.

The messages will be logged in output window. See here the check box Continue Execution which is self explanatory. If you uncheck this then the breatpoint would be hit as normal and pause the execution. So lets run the program and see the output window

I have provaide value 7. Here you can see that the value got printed here for each loop iteration. This is quite useful if number are pretty high.

Debugging is also get tricky in case mutli-threading and asynchronous programming scenarios which is pretty common nowadays.

There are few others pseudo variables available which can be used display various other useful information as

Hope you have enjoyed the post.

Cheers,
Brij

How to know the version of MVC of an Existing Project

Hello All,

This is one of the common questions which we see often in various forums. Even I have struggled to find the exact version of the MVC earlier. It becomes more tricky as Micrososft releases new MVC versions at regular interval. Earlier each new release was a major release with release number like MVC 1, MVC 2, MVC 3, MVC 4,MVC 5 but recently we see new releases with minor version like MVC 5.1, MVC 5.2 and even now with build number like the upcoming one ASP.NET MVC 5.2.4 (while previous one 5.2.3). It also become more problematic sometimes when we upgrade the mvc version.

Note – The version of a software is normally denoted by four number separated by dots as x.x.x.x which is as Major.Minor.Build.Revision.

There are many ways to find the specific version. We will discuss few common ones here

1- The simplest way to open Web.Config file and look for System.Web.Mvc, you could see similar as

Here 5.2.3 is the current version.

2- We can check the references in the solution explorer, find out the System.Web.Mvc, right click on it and select properties as

3- If your project contain packages.config (normally every project has it), then we can find the version from here easily.     Search for Microsoft.AspNet.Mvc and you should find something as

4- We can get the MVC version programatically based on the need as

5- There is a nuget package available which provides lots of useful information named MVCDiagnostics which adds a     page  named mvcdiagnostics.aspx which displays other useful information along with MVC version. This package could be   very useful if you are upgrading to new version and facing issues. The page looks as

I have not included the complete page for brevity but lot more details are availble on this page.

Package can be installed from here

This is quick post on of the common questions. Hope you find it useful.

Cheers,
Brij

Wish you all A Very Happy New Year -2018

As the first dawn of the new year arrives, I want to take this opportunity to Wish all my blog visitors, readers and followers a very Happy New Year 2018. As by each passing day, time is becoming more exciting, challenging, fast paced with lots of new opportunities, I wish everyone would achieve lot more than expected.

2017 has been a very happening year to me as I was travelling multiple places, my course on ASP.NET Core Web API is doing great and last but not the least, my MVP got renewed 7th time. Thanks a ton to all of you for your conituous support and feedback.

Again, A very happy new year to all of you.

Cheers,
Brij

Presented in Cleveland .NET User Group on ASP.NET Performance tips

Hello All,

Recently I presented in Cleveland C#/VB.NET User group on my favorite topic ASP.NET. I was amazed with the response as it was a full house event even in the holiday season. The event took place on 28th Dec 2017 at Indepedence (Cleveland) ohio. I discussed “10 Tips to Make ASP.NET Apps Faster” which was loaded with cool Demos. Here is a glimpse of the room

 

I had lot of fun speaking there. Please find the slides here

Thanks a lot to the all the attendees and Cleveland .NET user group for hosting me as a Guest Speaker.

Cheers,
Brij

Inheritance with JavaScript

This post is in continuation in my last post.  In my last post, I discussed various ways to create custom object in JavaScript. I’ll advise you to go through that if you didn’t get a chance to have a look then you can go through it. Please find the link below

Various ways to Create custom objects in JavaScript

In this post, We will discuss, how we can use other features of Object Oriented concepts in JavaScript. Today I’ll discuss one of the main concepts of Object Orient Programming that is Inheritance.

So how can we use Inheritance with JavaScript ?

Various ways and plugins are available that provides similar ways to use Inheritance that we have used in other object oriented language. But the prototype based Inheritance is used most.

JavaScript is a object based language that is based upon Prototype based programming. It is free from Class and completely rely on objects only .

Did you hear earlier  that What is Prototype based language or what is Prototype based programming?

I would say this is just another way to provide object oriented feature by a language. As per wiki

Prototype-based programming is a style of object-oriented programming in which classes are not present, and behavior reuse (known as inheritance in class-based languages) is performed via a process of cloning existing objects that serve as prototypes. This model can also be known as classless, prototype-oriented or instance-based programming. Delegation is the language feature that supports prototype-based programming”.

So let’s start learning. To create a Class in JavaScript, we are required to create a function  that we also used to call a Constructor. I’ll use the word constructor in my further discussion. So Let’s create a Constructor called person

         function Person() {
             this.ToString = function () { alert('I am a Person'); }
             this.DisplayResidence = function () { alert('I stay near my office'); }
         }

As in my last post, I mentioned that Person is a nested function. As you can see that here we have following two functions in the Person constructor.

  1. ToString
  2. DisplayResidence

So let’s create a new object and display it

function DisplayObject()
{
var objPerson = new Person(); // Line- 1 Creates the instance of Person
objPerson.ToString();  // Line- 2
objPerson.DisplayResidence(); // Line- 3
}

Here both display as expected . Line 2 – I am a Person and Line 3 – I stay near my office

Now let’s say we want to create a constructor Employee as

         function Employee() {
             this.ToString = function () { alert('I am an employee'); }
             this.DisplayRole = function () { alert('My role is development and implementation'); }
         }

As you can see it has two methods ToString and DisplayRole. Now how can Employee inherit the properties/methods of Person. It can be done by writing as

Employee.prototype = new Person();

Now the employee has the properties of person as well. Now it has three methods

  • ToString()
  • DisplayResidence()
  • DisplayRole()

Let’s examine it by the method

         function DisplayObject() {
                var objPerson = new Person(); // Line- 1: Calles constrouctor Person to create an instance and assign it to objPerson
                objPerson.ToString(); // Line- 2: Calles ToString method of Person
                objPerson.DisplayResidence(); // Line- 3: Calles ToString method of Person

                var objEmployee = new Employee();  // Line- 4: Calles constrouctor Employee to create an instance and assign it to objEmployee
                objEmployee.ToString(); // Line- 5: Calles ToString method of Person
                objEmployee.DisplayResidence(); // Line- 6:  Calles ToString method of Person
                objEmployee.DisplayRole(); // Line- 7:  Calles ToString method of Person

                alert(objPerson instanceof Person);  // Line- 8:  Checks the type of objPerson
                alert(objEmployee instanceof Person);  // Line- 9:  Checks the type of objEmployee
         }

Let’s discuss it by Line numbers

Line 2 and Line 3- same as discussed above

Line 5- What it will display ? It displays I am an employee because ToString is available at both current and parent. But because the objEmployee holds the instance of derived class so the overridden method is called.

Line 6- Here DisplayResidence is not defined in Employee so it calls the base class(Person) method and displayed.

Line 7-  DisplayRole is added in Employee object only and it shows ‘My role is development and implementation‘.

Line 8 – To check more on the type I added the last two lines. As objPerson is instance of Person only so it shows true.

Line 9 – As Employee inherits Person so it also shows true but if you delete the below line ….

<br />Employee.prototype = new Person();<br />

then it’ll show false as it does not inherit person any more.

Now you must have got enough Idea about prototype based inheritance in JavaScript.

There is one more way to add a method to and existing constructor as Person has two methods and  that we defined as nested class. You can write that in the following way as well

         function Person() {
         }
         Person.prototype.ToString = function () { alert('I am a Person'); }
         Person.prototype.DisplayResidence = function () {alert('I stay near my office');}

Now the question arises,  how Inheritance works in JavaScript.

Whenever we create an instance using the new Operator, It creates all the properties/methods and also has internally a variable called __proto__ (double underscore at both side) this is the variable which is responsible for the inheritance feature. So let’s say I created a instance of Employee as

var objEmployee = new Employee();

It’ll be having two methods/properties as defined and on __proto__ as

  1. ToString
  2. DisplayRole
  3. __proto__

Just because I have written also as

Employee.prototype = new Person();

The __proto__ variable gets assigned to the person instance. This __proto__ used to determine the prototype chain and return the property values. This allows us to access the base class methods and public properties.

As I talked about prototype chain, means as soon as I assign

Employee.prototype = new Person();

a proto variable gets available to us that can be be further used for inheritance. So lets create another constructor as

         function TeamLead() {
             this.ToString = function () { alert('I am a Manager.'); }
             this.DisplayRole = function () { alert('I rarely code but do lot of code reviews'); }
             this.DisplayMeetings = function () { alert('I have 3 meetings scheduled daily'); }
         }

Now as soon as I’ll create an instance using new operator then instance will be have the properties

  1. ToString
  2. DisplayRole
  3. DisplayMeetings
  4. __proto__

Now if we write the code for inheritance as

TeamLead.prototype = new Employee();

It can access all the properties in the hierarchies. We can check the type of instances as

 function DisplayObject() {
             var objTeamLead = new TeamLead();
             alert(objTeamLead instanceof Person);  // returns true because TeamLead inherits base class Person
             alert(objTeamLead instanceof Employee);  // returns true because TeamLead inherits  base class Employee
             alert(objTeamLead instanceof TeamLead); // returns true as expected
             }

You can see the results and they are expected

Let’s see the prototype chain as discussed earlier

         function DisplayObject() {
             var objTeamLead = new TeamLead();

             // Also here I'll show, How the prototype chain works
             alert(objTeamLead.__proto__ == TeamLead.prototype); // returns true because it represents the same prototype
             alert(objTeamLead.__proto__.__proto__ == Employee.prototype);  // returns true because second level __proto__ belongs to Employee.prototype
             alert(objTeamLead.__proto__.__proto__.__proto__ == Person.prototype);  // returns true because third level __proto__ belongs to Employee.prototype
         }

As you can see that actually __proto__ variable is actually the key for the inheritance.

Now you all must have got enough Idea about Prototype based programming and how we can use inheritance with JavaScript.

Do share your feedback.

Happy Coding,
Brij