c# and .NET Interview Questions Shivprasad Koirala

c# and .NET interview questions Shivprasad Koirala

c# and . NET interview questions Shivprasad Koirala c# and .NET interview questions Friday, June 17, 2011

Learn MVC (Model view controller) Step by Step in 7 days – Day 1

About Me

Shivprasad Koirala Visit us @ www.questpond.com or call us at 02266752917 View my complete profile

Contents So, what’s the agenda? So why MVC when ASP.Net behind code was so good? Problem number 1:- UNIT Testing Problem 2 :- The reality of separation of code and UI Our HERO MVC (Model, view and controller) Pre-requisite for MVC Lab1:- Creating a simple hello world ASP.NET MVC Application Video demonstration for Lab 1 Step1:- Create project Step 2:- Add controller http://computerauthor.blogspot.com/ (1 of 36) [6/25/2011 4:48:52 PM]


Step 3:- Add View Step 4:- Run the application So what’s in the next Lab? Lab2:- Passing data between controllers and views Video demonstration for Lab 2 Step1:- Create project and set view data Step 2:- Display view data in the view. So what’s in the next Lab? Lab 3:- Creating a simple model using MVC Video demonstration for Lab 3 Step1:- Create a simple class file Step2:- Define the controller with action Step3:- Create strongly typed view using the class Step 4 :- Run your application So what’s in the next Lab? Lab 4:- Creating simple MVC data entry screen Video demonstration for Lab 4 Step1:- Creating your data entry ASPX page Step2:- Creating the controller Step3:- Create the view to display the customer object Step 4:- Finally run the project So what’s in the next Lab? Lab 5:- using HTML helper to create views faster Step 1:- Create the Customer class Step2:- Creating the input HTML form using helper classes Step 3:- Create a strong typed view by using the customer class Step4:- Creating the controller class. What’s for the second day?

So, what’s the agenda? As the article name says learn MVC, so the agenda is simple we are going to learn ASP.NET MVC • in 7 days. The way we will learn MVC in this series of article is by doing Labs, looking at detail steps of how to achieve those labs and also looking at demonstrative videos.

http://computerauthor.blogspot.com/ (2 of 36) [6/25/2011 4:48:52 PM]


This complete article is divided in to 7 days with 42 hands on labs and every day we will do 6 labs which will help us achieve our goals. So get ready for day 1. In day1 below is our agenda we will start with introduction, do a simple hello world and finally in the 6th lab we will create a simple customer data entry screen using HTML helper classes.

You can watch my .NET interview questions and answers videos on various sections like WCF, Silver light, LINQ, WPF, Design patterns, Entity framework etc

So why MVC when ASP.Net behind code was so good?

I am sure all ASP.NET love the behind code concept. Accepting something new like MVC will not convince them. So let’s analyze the problems with the current behind code stuff. When we generally talk about ASP.NET application built on tiered architecture they are divided in four parts UI (ASPX pages), behind code (ASPX.CS pages), Middle tier (.NET classes) and finally Data layer. If you see from the aspect of code distribution major code which has logic is in the middle tier or in the behind code (APX.CS files). The UI or ASPX files are HTML files which is more of UI design and data access logic are pretty much standard components like enterprise data blocks, entity data contexts etc.



Let’s try to analyze the problems.

Problem number 1:- UNIT Testing

From the aspect of unit testing we can exclude the data logic and the UI HTML. The data logic classes are already time tested components like enterprise data block, entity data context or LINQ data context. So we really do not have to put lot of effort on testing the DAL separately. In case you have custom data access layer it will be still easy to test them as they are simple .NET classes. There is no logic in testing on ASPX HTML as such it’s more of look and feel. The middle tier is again a simple .NET class like data logic so you can easily do unit testing using VSTS or NUNIT. Now comes the most important one the behind code. The behind code has lot of action and testing them is one of the most important things. The only way to invoke these codes are by doing manual test. From a longer run perspective this would not be a great choice. Even though www.microsoft.com always boasted about how the ASP.NET behind code was separate from the UI, in practical sense it’s very difficult to decouple an ASP.NET behind code and do unit testing on them. The ASP.NET behind code is completely tied up with ASP.NET Httpcontext object which makes unit testing very difficult. Just think how do I unit test the below behind ASP.NET code. How do I create a Http context object , how do I simulate the sender and eventargs objects of the button clicks etc. FYI: - Many developers would talk about mock test, rhino mocks etc but still its cryptic and the complication increases with session variables, view data objects, ASP.NET UI controls creating further confusion.



Problem 2 :- The reality of separation of code and UI

As said previously the ASPX and the ASPX.CS cannot be decoupled in reality thus reducing reusability. Yes, Microsoft did said first that the behind code is different and the UI is different but then they are probably separate physical files only and one cannot just exist without other. For instance let’s say the same button click code when called via HTTP POST should display using displayinvoice.aspx and when called via HTTP GET should display in tree view. In other words we would like to reuse the behind code. Just think how can we do the same using the current behind code.

Our HERO MVC (Model, view and controller)

That’s where MVC comes to rescue. The behind code is moved to a simple .NET class called as controller. Any user request first comes to the controller class, the controller class then invokes the model and attaches the model to the view for display to the end user.



As this controller class is a simple .NET class we can reuse and also do unit testing easily. So let’s see how we can create MVC application using MVC template provided by visual studio.

Pre-requisite for MVC

Before we start the day lets ensure that you have all the ingredients to create a MVC application. • Visual Studio 2010 or the free Visual Web Developer 2010 Express. These include ASP.NET MVC 2 template by default. • Visual Studio 2008 SP1 (any edition) or the free Visual Web Developer 2008 Express with SP1. These do not include ASP.NET MVC 2 by default; you must also download and install ASP.NET MVC 2 from http://www.asp.net/mvc/ . So once you have all your pre-requisite its time to start with the first lab.

Lab1:- Creating a simple hello world ASP.NET MVC Application

In this lab we will create a simple hello world program using MVC template.So we will create a simple controller, attach the controller to simple index. aspx page and view the display on the browser.

Video demonstration for Lab 1

In case you want spend more time with your family rather than reading the complete article you can watch the below 5 minute youtube video.



Step1:- Create project

Create a new project by selecting the MVC 2 empty web application template as shown in the below figure.

Once you click ok, you have a readymade structure with appropriate folders where you can add controllers, models and views.



Step 2:- Add controller

So let’s go and add a new controller as shown in the below figure.

Once you add the new controller you should see some kind of code snippet as shown in the below snippet. public class Default1Controller : Controller { // // GET: /Default1/ public ActionResult Index() { return View(); } } http://computerauthor.blogspot.com/ (8 of 36) [6/25/2011 4:48:52 PM]


Step 3:- Add View

Now that we have the controller we need to go and add the view. So click on the Index function which is present in the control and click on add view menu asshown in the below figure.

The add view pops up a modal box to enter view name which will be invoked when this controller is called as shown in the figure below. For now keep the view name same as the controller name and also uncheck the master page check box.

Once you click on the ok button of the view, you should see a simple ASPX page with the below HTML code snippet. In the below HTML code snippet I have added “This is my first MVC application”. http://computerauthor.blogspot.com/ (9 of 36) [6/25/2011 4:48:52 PM]


Index
This is my first MVC application

Step 4:- Run the application

If you do a CNTRL + F5 you should see a error as shown in the below figure.This error is obvious because we have not invoked the appropriate controller /action.

If you append the proper controller on the URL you should be able to see the proper view.

So what’s in the next Lab?

Now that we have created a simple MVC hello world, it’s time to see how we can pass data from controllers to views. The first hit comes to the http://computerauthor.blogspot.com/ (10 of 36) [6/25/2011 4:48:52 PM]


controller which will load your business objects or model and you would like to transfer these objects to the view to display them.

Lab2:- Passing data between controllers and views

The controller gets the first hit and loads the model. Most of the time we would like to pass the model to the view for display purpose. As an ASP.NET developer your choice would be to use session variables, view state or some other ASP.NET session management object. The problem with using ASP.NET session or view state object is the scope. ASP.NET session objects have session scope and view state has page scope. For MVC we would like to see scope limited to controller and the view. In other words we would like to maintain data when the hit comes to controller and reaches the view and after that the scope of the data should expire. That’s where the new session management technique has been introduced in ASP.NET MVC framework i.e. ViewData.

Video demonstration for Lab 2

Below is a simple youtube video which demonstrates the lab for view data. In this video we will see how we can share data between controller and the view using view data. So we will create a simple controller, record the current data in a view data variable and then display the same in the view using the percentage tag.

Step1:- Create project and set view data http://computerauthor.blogspot.com/ (11 of 36) [6/25/2011 4:48:52 PM]


So the first step is to create a project and a controller. In the controller set the viewdata variable as shown in the below code snippet and kick of the view. public class DisplayTimeController : Controller { // // GET: /DisplayTime/ public ActionResult Index() { ViewData["CurrentTime"] = DateTime.Now.ToString(); return View(); } }

Step 2:- Display view data in the view.

The next thing is to display data in the view by using the percentage tag. One important point to note is the view does not have a behind code. So to display the view we need to use the <%: tag in the aspx page as shown in the below code snippet.
<%: ViewData["CurrentTime"] %>


So now that we know how to pass data using view data, the next lab is to create a simple model and see all the 3 MVC entities (i.e. model, view and controller) in action.

Lab 3:- Creating a simple model using MVC

In this lab we will create a simple customer model, flourish the same with some data and display the same in a view.

Video demonstration for Lab 3 Below is a video demonstration for the same.

Step1:- Create a simple class file

The first step is to create a simple customer model which is nothing but a class with 3 properties code, name and amount. Create a simple MVC project, right click on the model folder and click on add new item as shown in the below figure. http://computerauthor.blogspot.com/ (12 of 36) [6/25/2011 4:48:52 PM]


From the templates select a simple class and name it as customer.

Create the class with 3 properties as shown in the below the code snippet. public class Customer { private string _Code; private string _Name; private double _Amount; public string Code { set { _Code = value; } get { return _Code; } } public string Name { get { return _Name; } set http://computerauthor.blogspot.com/ (13 of 36) [6/25/2011 4:48:52 PM]


{ _Name = value; } } public double Amount { set { _Amount = value; } get { return _Amount; } } }

Step2:- Define the controller with action

The next step is to add the controller and create a simple action display customer as shown in the below code snippet. Import the model namespace in the controller class. In the action we created the object of the customer class, flourished with some data and passed the same to a view named as “DisplayCustomer” public class CustomerController : Controller { ….. …. public ViewResult DisplayCustomer() { Customer objCustomer = new Customer(); objCustomer.Id = 12; objCustomer.CustomerCode = "1001"; objCustomer.Amount = 90.34; return View("DisplayCustomer",objCustomer); } }

Step3:- Create strongly typed view using the class

We need to now join the points of MVC by creating views. So right click on the view folder and click add view. You should see a drop down as shown in the below figure. Give a view name, check create a strongly typed view and bind this view to the customer class using the dropdown as shown in the below figure.



The advantage of creating a strong typed view is you can now get the properties of class in the view by typing the model and “.” as shown in the below figure.

Below is the view code which displays the customer property value. We have also put an if condition which displays the customer as privileged customer if above 100 and normal customer if below 100.
The customer id is <%= Model.Id %>
The customer Code is <%= Model.CustomerCode %>
<% if (Model.Amount > 100) {%> This is a priveleged customer <% } else{ %> This is a normal customer <%} %>

Step 4 :- Run your application http://computerauthor.blogspot.com/ (15 of 36) [6/25/2011 4:48:52 PM]


Now the “D” thing, hit cntrl + f5 and pat yourself for one more lab success.


In this sample we flourished the customer object from within the controller,in the next lab we will take data from an input view and display the same. Inother words we will see how to create data entry screens for accepting data from views.

Lab 4:- Creating simple MVC data entry screen

Every project small or big needs data entry screens. In this lab we will create a simple customer data entry screen as shown in the below figure using MVC template.

As soon as the end user enters details and submits data it redirects to a screen as shown below. If he entered amount is less than 100 it displays normal customer or else it displays privileged customer.



Video demonstration for Lab 4 Below is a simple video demonstration for this lab.

Step1:- Creating your data entry ASPX page

The first step is to create the data entry page using the simple HTML form action tag as shown in the below code snippet. The most important point to note in the below code snippet is that the action is pointing to the controller action i.e ‘DisplayCustomer’.
Enter customer id :-
Enter customer code :-
Enter customer Amount :-

Step2:- Creating the controller

The above defined form action will post to the controller class and on the function “DisplayCustomer”. So we need to get the data from the HTML controls, flourish the object and send the object to the view. Below is the code snippet of displaycustomer which flourishes the customer object by collecting data from request.form and sends the object to the view ‘displaycustomer. http://computerauthor.blogspot.com/ (17 of 36) [6/25/2011 4:48:52 PM]


public class CustomerController : Controller { ….. …. [HttpPost] public ViewResult DisplayCustomer() { Customer objCustomer = new Customer(); objCustomer.Id = Convert.ToInt16(Request.Form["Id"].ToString()); objCustomer.CustomerCode = Request.Form["Id"].ToString(); objCustomer.Amount = Convert.ToDouble(Request.Form["Amount"].ToString()); ; return View("DisplayCustomer", objCustomer); } }

Step3:- Create the view to display the customer object

The next step is to create the “DisplayCustomer” view.So right click on the view folder and click add view. You should see a drop down as shown in the below figure. Give a view name, check create a strongly typed view and bind this view to the customer class using the dropdown as shown in the below figure.

The advantage of creating a strong typed view is you can now get the properties of class in the view by typing the model and “.” as shown in the below figure.



Below is the view code which displays the customer property value. We have also put an if condition which displays the customer as privileged customer if above 100 and normal customer if below 100.
The customer id is <%= Model.Id %>
The customer Code is <%= Model.CustomerCode %>
<% if (Model.Amount > 100) {%> This is a priveleged customer <% } else{ %> This is a normal customer <%} %>

Step 4:- Finally run the project

Final step is to run the project and see the output.

You should be also able to test above 100 and below 100 scenarios



So what’s in the next Lab? In this lab we created a simple data entry screen which helped us flourish the customer object. This customer object was then passed to the view for display. If you closely watch the current lab we have done lot of coding i.e. creating the HTML screens , flourishing the object etc. It would be great if there was some kind of automation. In the next lab we see how HTML helper classes help to minimize many of these manual coding and thus increasing productivity.

Lab 5:- using HTML helper to create views faster In our previous lab we created a simple customer data entry screen. We completed the lab successfully but with two big problems:• The complete HTML code was written manually. In other words, less productive. It’s like going back to dark ages where developers used to write HTML tags in notepad.
Enter customer id :-
Enter customer code :-
Enter customer Amount :-

• Added to it lot of manual code was also written in the controller to flourish the object and send data to the MVC view. public class CustomerController : Controller { ….. …. [HttpPost] public ViewResult DisplayCustomer() { Customer objCustomer = new Customer(); objCustomer.Id = Convert.ToInt16(Request.Form["Id"].ToString()); objCustomer.CustomerCode = Request.Form["Id"].ToString(); objCustomer.Amount = Convert.ToDouble(Request.Form["Amount"].ToString()); ; return View("DisplayCustomer", objCustomer); http://computerauthor.blogspot.com/ (20 of 36) [6/25/2011 4:48:52 PM]


} } In this lab we will see how to use MVC HTML helper classes to minimize the above manual code and increase productivity

Step 1:- Create the Customer class Create a simple customer class , please refer Lab 5 for the same.

Step2:- Creating the input HTML form using helper classes

HTML helper classes have readymade functions by which you can create HTML controls with ease. Go to any MVC view and see the intellisense for HTML helper class you should see something as shown in the below figure.

By using HTML helper class you can create any HTML control like textbox, labels, list box etc just by invoking the appropriate function. In order to create the form tag for HTML we need to use “Html.BeginForm” , below goes the code snippet for the same. <% using (Html.BeginForm("DisplayCustomer","Customer",FormMethod.Post)) {%> -- HTML input fields will go here <%} %> The above code will generate the below HTML
….. …..
The HTML helper “beginform” takes three input parameters action name (Method inside the controller), controller name (actual controller name) and HTTP posting methodology (Post or GET).



If you want to create a text box, simply use the “TextBox” function of html helper class as shown in the below code. In this way you can create any HTML controls using the HTML helper class functions. Enter customer id :- <%= Html.TextBox("Id",Model)%>
The above code snippet will generate the below HTML code. Enter customer id :-
To create a data entry screen like the one shown below we need to the use the below code snippet.

<% using (Html.BeginForm("DisplayCustomer","Customer",FormMethod.Post)) { %> Enter customer id :- <%= Html.TextBox("Id",Model)%>
Enter customer code :- <%= Html.TextBox("CustomerCode",Model) %>
Enter customer Amount :- <%= Html.TextBox("Amount",Model) %>
<%} %>

Step 3:- Create a strong typed view by using the customer class

So once you have created the view using the HTML helper classes it’s time to attach the customer class with view , please refer lab 5 for the same.

Step4:- Creating the controller class.

The final thing is the controller code. The controller code now becomes very simple. The customer object will be auto flourished as we have used the HTML helper classes. You will create the controller class as we did in Lab 4 but we do not need to write any kind of code for connecting the HTML screens with controller, it’s all hidden and automated. [HttpPost] public ActionResult DisplayCustomer(Customer obj) { return View(obj); } Enjoy your output for different condition of customer amount entered.



So have a toast of beer for completing your first day of MVC labs.

What’s for the second day?

In the next labs we will talk about URL routing, ease of MVC unit testing, MVC Controller attributes and lot more. The next lab will bit more advanced as compared to the first day, so take rest and I need to work hard to get you the second day labs.

Posted by Shivprasad Koirala at 6:37 AM 0 comments

Saturday, June 11, 2011

C# interview questions :- In what scenarios do we define a constructor private ? http://computerauthor.blogspot.com/ (23 of 36) [6/25/2011 4:48:52 PM]


We define a constructor private in the following scenarios:• We want to restrict the client to not create objects. • In case of singleton patterns where we want only instance of the object to be created. Below is a simple video which explains the above concept practically.

Please click here to see more C# interview questions Posted by Shivprasad Koirala at 6:11 AM 0 comments

.NET interview questions :- What are stack , heap , value , reference types , boxing and unboxing ? Stack and heap are memory types in an application. Stack memory stores data types like int , double , Boolean etc. While heap stores data types like string and objects. For instance when the below code runs the first two variables i.e. “i” and “y” are stored in a stack and the last variable “o” is stored in heap. void MyFunction() { int i = 1; // This is stored in stack. int y = i; // This is stored in stack. object o = null; // This is stored in heap. } // after this end the stack variable memory space is reclaimed while // the heap memory is reclaimed later by garbage collector. Value types contain actual data while reference types contain pointers and the pointers point to the actual data. Value types are stored on stack while reference types are stored on heap. Value types are are your normal data types like int , bool , double and reference types are all objects. When value type is moved to a reference type it’s called as boxing. The vice-versa is termed as unboxing. Attaching to the above one more c# interview which comes up is What is boxing and unboxing , below is the video which explains the same. http://computerauthor.blogspot.com/ (24 of 36) [6/25/2011 4:48:52 PM]


Please click here to see more C# interview questions


Thursday, June 9, 2011

.NET interview questions :- What are regular expressions in .NET ? Do view our 15 minutes video on regex as below

C# Regex or regular expression helps us to describe complex patterns in texts. Once you have described these patterns you can use them to do searching, replacing, extracting and modifying text data. http://computerauthor.blogspot.com/ (25 of 36) [6/25/2011 4:48:52 PM]


Below is a simple sample of how to implement regex . The first step is to import the namespace for regular expressions. using System.Text.RegularExpressions; The next thing is to create the regex object with the pattern. The below pattern specifies to search for alphabets between a-z with 10 length. Regex obj = new Regex(“[a-z]{10}”); Finally search the pattern over the data to see if there are matches. In case the pattern is matching the ‘IsMatch’ will return true. MessageBox.Show(obj.IsMatch(“shivkoirala”).ToString()); Please click here to see more C# interview questions Regards, Visit Authors blog for more .Net / C# interview questions


Monday, June 6, 2011

What is WCF One way contract ? See 500 videos on c# and .NET interview questions Posted by Shivprasad Koirala at 10:03 PM 0 comments

Wednesday, June 1, 2011

Demo of Button and LinkButton control in ASP.NET See 500 videos on c# and .NET interview questions and ASP.NET interview questions Posted by Shivprasad Koirala at 10:29 PM 0 comments

Tuesday, May 31, 2011

.NET/ASP.NET interview Questions - Show us simple insert, http://computerauthor.blogspot.com/ (26 of 36) [6/25/2011 4:48:52 PM]


update and delete operation using LINQ? Answer: Let us assume that we have the following table of Student with their respective fields.

First open visual studio > New > project > select ASP.NET empty web application. Add > New item > select Web Form and create a simple form like below.

Once you have done creating the form, now you have to add LINQ to SQL Classes in your project. Add > New item > select LINQ to SQL Classes. As soon as you click on add a new window will appear from that just click on server explorer expand the data connection and select your database then drag and drop the table on the .dbml file like below diagram.



Now you have to add a class library file in your project. Add > New item > select Class. usingSystem.Data.Linq; usingSystem.Data.Linq.Mapping; namespaceLinq_to_insert { [Table(Name="Student")] publicclassClass1 { privatestring _Name; privatestring _Add; publicstring Name { get{ _Name = value;} get{return _Name;} } publicstring Add { set{ _Add = value; } get{return _Add;} } } }

Write code for insert update and delete with their respective buttons. For adding record. protectedvoidbtnAdd_Click(object sender, EventArgs e) { DataClasses1DataContextObjDataContext = newDataClasses1DataContext(); StudentObjStud = newStudent(); ObjStud.StudentAdd = TextBox2.Text; ObjStud.StudentName = TextBox1.Text.ToString(); ObjDataContext.GetTable().InsertOnSubmit(ObjStud); ObjDataContext.SubmitChanges(); Response.Write("Record Successfully Inserted"); http://computerauthor.blogspot.com/ (28 of 36) [6/25/2011 4:48:52 PM]


}

For updating record. protectedvoidbtnUpdate_Click(object sender, EventArgs e) { DataClasses1DataContextObjDataContext = newDataClasses1DataContext(); StudentObjStud = newStudent(); string Name1 = TextBox1.Text; string Address = TextBox2.Text; var Update = ObjDataContext.Students.Single(p =>p.StudentName == Name1); Update.StudentAdd = Address; ObjDataContext.SubmitChanges(); Response.Write("Record Successfully Updated"); }

For deleting record. protectedvoidbtnDelete_Click(object sender, EventArgs e) { DataClasses1DataContextObjDataContext = newDataClasses1DataContext(); StudentObjStud = newStudent(); string Name1 = TextBox1.Text.ToString(); var delete = ObjDataContext.Students.Single(s =>s.StudentName == Name1); ObjDataContext.Students.DeleteOnSubmit(delete); ObjDataContext.SubmitChanges(); Response.Write("Record Successfully deleted"); } You will be also interested in watching the below video, which are also asked in most of the interviews and favourable question of interviewers. &amp;amp;amp;amp;amp;amp;amp;amp;lt;br&amp;amp;amp;amp;amp;amp;amp;amp;gt;

Please click here to see more .NET and ASP.NET interview questions Regards, Visit Authors blog for more .NET and ASP.NET interview Question


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c# and .NET Interview Questions Shivprasad Koirala

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