Contents
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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();
}
}
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”.
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Index</title>
</head>
<body>
<div>
This is my first MVC application
</div>
</body>
</html>
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.
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 controller
which will load your business objects or model and you would like to transfer these objects to the view to display them.
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.
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.
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();
}
}
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.
<body>
<div>
<%: ViewData["CurrentTime"] %>
</div>
</body>
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.
In this lab we will create a simple customer model, flourish the same with some data and display the same in a view.
Below is a video demonstration for the same.
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.
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
{
_Name = value;
}
}
public double Amount
{
set
{
_Amount = value;
}
get
{
return _Amount;
}
}
}
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);
}
}
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.
<body>
<div>
The customer id is <%= Model.Id %> <br />
The customer Code is <%= Model.CustomerCode %> <br />
<% if (Model.Amount > 100) {%>
This is a priveleged customer
<% } else{ %>
This is a normal customer
<%} %>
</div>
</body>
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.
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.
Below is a simple video demonstration for this lab.
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’.
<form action="DisplayCustomer" method="post">
Enter customer id :- <input type="text" name="Id" /> <br />
Enter customer code :- <input type="text" name="CustomerCode" /><br />
Enter customer Amount :-<input type="text" name="Amount" /><br />
<input type="submit" value="Submit customer data" />
</form>
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.
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);
}
}
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.
<body>
<div>
The customer id is <%= Model.Id %> <br />
The customer Code is <%= Model.CustomerCode %> <br />
<% if (Model.Amount > 100) {%>
This is a priveleged customer
<% } else{ %>
This is a normal customer
<%} %>
</div>
</body>
Final step is to run the project and see the output.
You should be also able to test above 100 and below 100 scenarios
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.
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.
<form action="DisplayCustomer" method="post">
Enter customer id :- <input type="text" name="Id" /> <br />
Enter customer code :- <input type="text" name="CustomerCode" /><br />
Enter customer Amount :-<input type="text" name="Amount" /><br />
<input type="submit" value="Submit customer data" />
</form>
• 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);
}
}
In this lab we will see how to use MVC HTML helper classes to minimize the above manual code and increase productivity
Create a simple customer class , please refer Lab 5 for the same.
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
<form action="DisplayCustomer" method="post">
…..
…..
</form>
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)%> <br />
The above code snippet will generate the below HTML code.
Enter customer id :- <input type="text" name="Id" /> <br />
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)%> <br />
Enter customer code :- <%= Html.TextBox("CustomerCode",Model) %><br />
Enter customer Amount :- <%= Html.TextBox("Amount",Model) %><br />
<input type="submit" value="Submit customer data" />
<%} %>
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.
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.
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.
