What is difference between constants, read-only and, static?
Constants: The value can’t be changed
Read-only: The value will be initialized only once from the constructor of the class.
Static: Value can be initialized once.
What is the cross page post backing?
Asp.Net 2.0 fixed this with built-in features that allowed us to easily send information from one page to another.
Button control has property PostBackUrl that can be set to URL of any page in our ASP.Net WebSite where we want to transfer all form values to.
Along with that Asp.Net 2.0 Page class has a property PreviousPage that allows us to get reference to the Page object that initiated the postback (in other words to get the actual reference to the Page object of the aspx page on which user clicked the Submit button on a HTML form).
So for example lets create two sample pages in our Web Application:
SourcePage.aspx
DestinationPage.aspx
In SoucePage in Html form we will put two TextBox controls (one for First Name and one for Last Name) and one Button component and set its PostBackUrl property to "~/DestinationPage.aspx".
SourcePage.aspx:
<form id="form1" runat="server">
<div>
First Name: <asp:TextBox ID="FirstName" runat="server"></asp:TextBox><br />
Last Name: <asp:TextBox ID="LastName" runat="server"></asp:TextBox><br /><br />
<asp:Button ID="Button1" runat="server" Text="Submit To Destination Page" PostBackUrl="~/CrossPagePostbacks/DestinationPage.aspx" />
</div>
</form>
When our user clicks the Submit button, all the values from the HTML Form on SourcePage.aspx will be transfered to the DestinationPage.aspx and we will also be able to get reference to the SourcePage.aspx in our DestinationPage with the PreviousPage property like this:
So in our DestinationPage.aspx.cs code-behind we can easily access two TextBox controls on SourcePage.aspx and show them in two label controls like this:
protected void Page_Load(object sender, EventArgs e)
{
// first check if we had a cross page postback
if ( (PreviousPage != null) && (PreviousPage.IsCrossPagePostBack) )
{
Page previousPage = PreviousPage;
TextBox firstName = (TextBox)previousPage.FindControl("FirstName");
TextBox lastName = (TextBox)previousPage.FindControl("LastName");
// we can now use the values from TextBoxes and display them in two Label controls..
labelFirstName.Text = firstName.Text;
labelLastName.Text = lastName.Text;
}
}
You probably noticed that we first checked if PreviousPage property of current page (DestinationPage.aspx) is NOT NULL, this is done to avoid running our code in case that user opens our DestinationPage.aspx directly, without running a cross page postback.
Also here we checked the another PreviousPage property called IsCrossPagePostBack to see if we really had a CrossPagePostback.
(If Server.Transfer is used to redirect to this page, IsCrossPagePostBack property will be set to FALSE.
TIP: We can be completely sure that we have a real CrossPagePostback ONLY IF:
Page.PreviousPage is NOT NULL,
PreviousPage.IsCrossPagePostback is true
This important to check to avoid errors in code.
Now this is very useful and i'm sure you are eager to use this in your next project. But wait, we are not over yet!
Finding the controls on PreviousPage with FindControl method and type-casting them from object to their real type is a little messy.
It feels like there must be a better solution for this!
And here it is: We can use the <%@ PreviousPageType %> directive in the header of our DestinationPage.aspx like this
<%@ PreviousPageType VirtualPath="~/SourcePage.aspx" %>
to declare our previous page type, and then we can access Public properties of the PreviousPage without typecasting.
Now all we need to do is to create some public properties on our SourcePage.aspx.cs to expose data/Controls we want to the destionation page:
public partial class SourcePage : System.Web.UI.Page
{
public string FormFirstName
{
get { return FirstName.Text; }
}
public string FormLastName
{
get { return LastName.Text; }
}
}
And then we can change the Page_Load code in our DestinationPage.aspx to much cleaner code like this:
protected void Page_Load(object sender, EventArgs e)
{
// first check if we had a cross page postback
if ( (PreviousPage != null) && (PreviousPage.IsCrossPagePostBack) )
{
SourcePage prevPage = PreviousPage;
// we can now use the values from textboxes and display them in two Label controls..
labelFirstName.Text = prevPage.FormFirstName;
labelLastName.Text = prevPage.FormLastName;
}
}
SourcePage type used in the code is offcourse name of the partial class defined is SourcePage.aspx.cs that inherits System.Web.UI.Page that is automatically created for us when we created new WebForm in VisualStudio.
This code is much cleaner and easier to follow, there is no ugly typecasting, just simple property values to use to retrieve the data from previous page.
When should you use Abstract Class vs Interface while programming?
Ans: When we want that sub class must implement all the methods of base class. In such a situation we will implement the interface. In the other hand when we want only some method of base class in our sub class then use base class as abstract class.
What is the difference between application exception and system exception?
Ans: The difference between application exception and system exception is that system exceptions are thrown by CLR and application exceptions are thrown by applications.
What is the difference between authorization and authentication?
Ans: Authorization is a process of allowing or denying resources to particular user or record
Declaration of authorization is
<authorization>
<allow users=”Suresh, Sanjay”/>
<deny users=”Ramana, Rakesh”>
</authorization>
Sometimes authorization allows the unauthorized persons at that time we will use
<deny users=”?”/>
Authentication means
Authentication is a process where we identify the credentials of user i.e. username, password and create an identity to mention user as an authenticated.
What is the use of n-tier architecture and 3-tier architecture?
Check this article for 3-tier architecture 3 tier architecture example in asp.net
How to get the version of the assembly?
Ans: lbltxt.text=Assembly. GetExecutingAssembly().GetName().Version.ToString();
What is the location of Global Assembly Cache on the system?
Ans: c:\Windows\assembly
What is the serialization?
Ans: Serialization is a process of converting object into a stream of bites.
What is synchronization?
Ans: The mechanism needed to block one thread access to the data. If the data is being accessed by another thread.
Synchronization can be accessed by using system.monitor class
A monitor class methods are enter, exit, pulse for this lock statement is also used
Suppose if we need to synchronize some data at that time we need to place that data in this block
Lock
{
}
Whatever the data has been placed into the lock block that data has been blocked
What are the thread priority levels?
Ans: Thread priority levels are five types
0 - Zero level
1 - Below Normal
2 - Normal
3 - Above Normal
4 - Highest
By Default priority level is 2
What is the difference between .tostring(), Convert.tostring()?
Ans: The basic difference between them is “Convert” function handles NULLS while
“.ToString()” does not it will throw a NULL reference exception error. So as a good coding
practice using “convert” is always safe.
What is Collation?
Ans: Collation refers to a set of rules that determine how the data is sorted and compared.
What is the difference between Primary key and unique key?
Ans: Primary key does not allow the null values but unique key allows one null value.
Primary key will create clustered index on column but unique key will create non-clustered index by default.
How many web.config files are there in 1 project?
Ans: There might be multiple web.config files for a single project depending on the hierarchy of folders inside the root folder of the project, so for each folder we can use one web.config file
What is the difference between throw and throw ex?
What is the difference between view state and hidden field?
Ans: viewstate is secured hidden field is insecure
Viewstate will store large amount of data but hidden filed will store small amount of data.
What is the difference between binary serialization and xml serialization?
What is the Difference between read only and constant variables?
Ans: Read only can assign the values at runtime only.
Constant will assign the values at compile time only.
We cannot modify the both variable values.
What is static keyword in .Net?
Ans: Static is same as constant variable but we can change the value of static variable and we can access the variables without creating any instances
What is the use of business logic layer in 3-tier architecture in .net?
Ans: Though a web site could talk to the data access layer directly, it usually goes through another layer called the business layer. The business layer is vital in that it validates the input conditions before calling a method from the data layer. This ensures the data input is correct before proceeding, and can often ensure that the outputs are correct as well. This validation of input is called business rules, meaning the rules that the business layer uses to make “judgments” about the data.
However, business rules don’t only apply to data validation; these rules apply to any calculations or any other action that takes place in the business layer. Normally, it’s best to put as much logic as possible in the business layer, which makes this logic reusable across applications.
One of the best reasons for reusing logic is that applications that start off small usually grow in functionality. For instance, a company begins to develop a web site, and as they realize their business needs, they later decide to add a smart client application and windows service to supplement the web site. The business layer helps move logic to a central layer for “maximum reusability.”
Check this post introduction to 3-tier Architecture
What happens when I enter a URL in my browser and click enter?
You type in the URL and hit go. The browser needs to translate that URL www.somesite.com into an IP address so it knows what computer on the internet to connect to (That URL is just there to make it easier for us humans - kinda like speed-dial for phone numbers I guess). So your browser will see if it already has the appropriate IP address cached away from previous visits to the site. If not, it will make a DNS query to your DNS server (might be your router or your ISP's DNS server) - see http://en.wikipedia.org/wiki/Domain_name… for more on DNS. Once your browser knows what IP to use, it will connect to the appropriate webserver and ask for the page. The webserver then returns the requested page and your browser renders it to the screen.
The firewall will control connections to & from your computer. For the most part it will just be controlling who can connect to your computer and on what ports. For web browsing your firewall generally won't be doing a whole lot.
Your router (see http://en.wikipedia.org/wiki/Router ) essentially guides your request through the network, helping the packets get from computer to computer and potentially doing some NAT (see http://en.wikipedia.org/wiki/Network_add… ) to translate IP addresses along the way (so your internat LAN request can be transitioned onto the wider internet and back).
IP Addresses (see http://en.wikipedia.org/wiki/IP_address ) are unique addresses for computers that basically allow computers to find each other. Think of the IP address as a computer's well address or phone number, you've got to know someone's phone number before you can call them and you've got to know a computer's IP address before you can connect to it. Going back to the start - that's what those URLS and DNS make possible, you don't know John Doe's phone number so you look in the phone book; likewise your computer doesn't know yahoo.com's IP address so it looks in DNS.
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