Data Annotations

routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "myuser", action = "Index", id = UrlParameter.Optional }
);

using System.ComponentModel.DataAnnotations;
using System.Web.Mvc;
using System.ComponentModel.DataAnnotations.Schema;

[Required]
[StringLength(20, MinimumLength = 4, ErrorMessage = "Must be at least 4 characters long.")]
[Remote("checkusername", "myuser")]
public string username { get; set; }

[Required]
public string firstname { get; set; }

public string lastname { get; set; }

[Required]
public string address { get; set; }

[Required]
[DataType(DataType.PhoneNumber)]
[StringLength(10, MinimumLength = 10, ErrorMessage = "{0}: it should be 10 digits")]
public Nullable phone { get; set; }

[Required(ErrorMessage = "{0} required")]
[DataType(DataType.EmailAddress)]
[Display(Name = "Email")]
[RegularExpression(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", ErrorMessage = "Invalid email")]
[Remote("checkemail", "myuser", ErrorMessage = "Already in use!")]
[StringLength(100, ErrorMessage = "{0}: 100 is the limit")]
public string email { get; set; }

public Nullable isactive { get; set; }

[Required]
[DataType(DataType.Password)]
public string password { get; set; }

[Required]
[NotMapped]
[System.ComponentModel.DataAnnotations.Compare("password", ErrorMessage = "Password doesn't match.")]
[DataType(DataType.Password)]
public string confirmpassword { get; set; }

public JsonResult checkusername(string username)
{
var data = db.users.Where(p => p.username.Equals(username, StringComparison.CurrentCultureIgnoreCase)).FirstOrDefault();

if (data != null)
{
return Json("Sorry, this name already exists", JsonRequestBehavior.AllowGet);
}
else
{
return Json(true, JsonRequestBehavior.AllowGet);
}
}

public JsonResult checkemail(string email)
{
var result = true;
var user = db.users.Where(x => x.email == email).FirstOrDefault();

if (user != null)
result = false;

return Json(result, JsonRequestBehavior.AllowGet);
}

Difference between GET and POST

Both perform same action only. Using both we can able to transfer data from one application to another. Using get method we can able to view the information in URL itself, but using post we can able to transfer data over networks, so this is very secure. Post method data we can’t get it directly. But Get method data we can get easily.

We can’t able to transfer bulk of data using GET method. But using post method we can able to transfer bulk of data. Compare to GET method POST method is secure.

Self-join queries

Self-Join is a type of join which is used to join the same table by creating the second instance of the same table. So we join 2 instances of the same table in case of self-join. This type of join is used when there is the requirement to get the referenced data which is available in the same table.
e.g. A table contains EmpId, Ename and ManagerId
As the manager id is also an employee id. Now if we want that who is the manager of which employee. In this situation, we need to create the instance of the same table and get the required data as:

SELECT EMPID, ENAME, ENAME AS [MANAGER NAME]
FROM EMP E1, EMP E2
WHERE E1.EMPID= E2.MANAGERID

Anonymous methods in C#

The concept of anonymous method was introduced in C# 2.0. An anonymous method is inline unnamed method in the code. It is created using the delegate keyword and doesn’t required name and return type. Hence we can say, an anonymous method has only body without name, optional parameters and return type. An anonymous method behaves like a regular method and allows us to write inline code in place of explicitly named methods.

A Simple Anonymous Method Example

delegate int MathOp(int a, int b);
class Program
{
   //delegate for representing anonymous method
   delegate int del(int x, int y);
 
static void Main(string[] args)
{
   //anonymous method using delegate keyword
   del d1 = delegate(int x, int y) { return x * y; };
 
   int z1 = d1(2, 3);
   Console.WriteLine(z1);
}
}
//output:
6

Key points about anonymous method

1. A variable, declared outside the anonymous method can be accessed inside the anonymous method.


2. A variable, declared inside the anonymous method can’t be accessed outside the anonymous method.


3. We use anonymous method in event handling.


4. An anonymous method, declared without parenthesis can be assigned to a delegate with any signature.


5. Unsafe code can’t be accessed within an anonymous method.


6. An anonymous method can’t access the ref or out parameters of an outer scope.

Anonymous Method as an Event Handler

 <form id="form1" runat="server">
 < div align="center">
<h2>Anonymous Method Example</h2>
 <br />
 <asp:Label ID="lblmsg" runat="server" ForeColor="Green" Font-Bold="true"></asp:Label>
 <br /><br />
 <asp:Button ID="btnSubmit" runat="server" Text="Submit" /> 
 <asp:Button ID="btnCancel" runat="server" Text="Cancel" />
 </div>
 </form>

protected void Page_Load(object sender, EventArgs e)
{
   // Click Event handler using Regular method
   btnCancel.Click += new EventHandler(ClickEvent);
   // Click Event handler using Anonymous method
   btnSubmit.Click += delegate { lblmsg.Text=
          "Submit Button clicked using Anonymous method"; };
}
protected void ClickEvent(object sender, EventArgs e)
{
   lblmsg.Text="Cancel Button clicked using Regular method";
}

Interview questions

http://pawantechit.blogspot.in/2013/03/interview-question-for-3-6-year.html

http://www.interviewquestionspdf.com/2014/09/aspnet-interview-questions-and-answers.html

https://www.udemy.com/understand-nodejs/

https://www.udemy.com/learn-angularjs/

https://www.udemy.com/design-and-develop-a-killer-website-with-html5-and-css3/

User id : aagrawal ksl

Pwd: password234

http://www.dotnetspider.com/resources/44635-Interview-Questions-3-6-years-experienced-Net-professional.aspx

http://www.aspdotnet-suresh.com/2010/05/interview-questions-in-aspnetcnetsql.html

http://pawantechit.blogspot.in/2013/03/interview-question-for-3-6-year.html

http://pluralsight.com/training/Player?author=scott-allen&name=mvc4-building-m2-controllers&mode=live&clip=0&course=mvc4-building

http://www.dotnet-tricks.com/Tutorial/mvclist

Stored procedure vs inline query

Stored procedures are precompiled and cached so the performance is much better.

The choice of choosing stored procedures will not be performance but it will be more from the aspect of security and maintenance. Below are some of the points where stored procedures are definitely a plus over inline SQL.

Abstraction

By putting all your SQL code into a stored procedure, your application is completely abstracted from the field names, tables names, etc. So when you make changes in the SQL, you have less impact in your C# code.

Security

This is the best part where stored procedures again score, you can assign execution rights on users and roles.

Maintenance ease

Now because we have centralized our stored procedures any issue like fixing defects and other changes can be easily done in a stored procedure and it will be reflected across the installed clients. At least we do not need to compile and deploy DLLs and EXEs.

Centralized tuning

If we know we have a slow running stored procedure, we can isolate it and the DBA guys can performance tune it separately.

Cursors, temp table complications

Simple TSQLs are OK. But what if you have a bunch of statements with IF, ELSE, Cursors, etc? For those kind of scenarios, again stored procedures are very handy.

State management

A new instance of the Web page class is created each time the page is posted to the server. In traditional Web programming, this would typically mean that all information associated with the page and the controls on the page would be lost with each round trip.

To overcome this inherent limitation of traditional Web programming, ASP.NET includes several options. These features are as follows:

• View state


• Control state


• Hidden fields


• Cookies


• Query strings


• Application state


• Session state


• Profile Properties

 

https://msdn.microsoft.com/en-us/library/75x4ha6s.aspx

return types in mvc

Return View

This is a most common and very frequently used type. We see that we can pass eight parameters when we return the view. We can specify the view name explicitly or may not.

Return partial View

The concept of a partial view is very similar to the master page concept in Web Form applications. The partial view is nothing but  pagelet, that we can return from the controller and that merges with the main view and generates one concrete HTML page.

It may take 4 parameters to render in the partial view.

Redirect

This is equivalent to Response.redirect() or Server.Transfer() functions. It takes the URL path to be redirect , though we can use Response.Redirect() or Server.Transfer() in MVC too.

Redirect To Action

Sometimes it is necessary to call another action after completion of one action, this is very similar to a function call in traditional function oriented programming or Object Oriented Programming. It may take 6 parameters. The first parameter is very simple, only action name.

Return content

This is useful when we want to return a small amount of strings from a controller/action. It takes three parameters. The first one is a simple string and the remaining two are strings with little information.

Return JSON

This is very useful when we don't want an entire HTML page but only want a value. Generally in AJAX-based single-page applications we do not load an entire page again and again but load fresh data from the DB using AJAX. In this scenario we can return only a JSON object and in the success function of jQuery ajax (let's assume we are using the jQuery library to implement AJAX) we can just manipulate data.

Return JavaScript

When we wanted to return a JavaScript string , we may use this function. It takes only one parameter, the string only.

Return File

We are allowed to return a binary file if needed from a controller. It takes 6 parameters maximum.

user control vs custom control in c#

Custom Control	User Control
A loosely coupled control w.r.t code and UI	A tightly coupled control w.r.t code and UI
Derives from Control	Derives from UserControl
Defines UI in a ResourceDictionary	Defines UI as normal XAML
UI is skinable	Child controls are skinable
Has dynamic layout	Has static layout
UI can be changed in different projects	UI is fixed and can't have different looks in different project
Has full toolbox support, Jst drag n drop from toolbox	Can't be added to the toolbox, Jst drag n drop from sol’n explorer to page(aspx)
Defines a single control	Defines a set of controls
More flexible	Not very flexible like a Custom Control
Reusability of control (extend functionality of existing control), Designed so that it can be used by more than one application	Reusability web page, Designed for single-application scenarios
Compiled into dll	Not compiled into dll
Creation is similar to the way Web Forms pages are created; well-suited for rapid application development (RAD)	Writing involves lots of code because there is no designer support

Button, CheckBox, TextBox etc., even a UserControl is nothing but a Custom Control. You can easily load them inside a XAML page.

Custom Controls are compiled into a DLL assembly and can be reused in multiple places very easily. You have total control over the code, thus gives you more flexibility to extend the behaviour. Once you build and add a reference of the custom control in your project, you can find it in the toolbox. Thus, you will be able to drag and drop the control in your Design view and start working with it very easily.

• When you have a rapid and fixed content in your UI, use UserControl.


• When you want to separate some basic functionality of your main view to some smaller pieces with reusability, use UserControl.


• When you want to use your control in different projects and each project may want to change the look, use CustomControl.


• When you want to implement some additional functionality for a control, create a CustomControl derived from the base control.


• When you want to apply themes to your controls, use CustomControl.


• When you want to add toolbox support for your control, so that your user will be able to do drag and drop to the designer, use CustomControl.

For user control:

<%@ Register TagPrefix="UC" TagName="TestControl" Src="test.ascx" %>

For custom control:

<%@ Register TagPrefix="CC " Namespace=" CustomServerControlsLib " Assembly="CustomServerControlsLib " %>

 

Linq query on datatable

var results = from myRow in myDataTable.AsEnumerable()
where myRow.Field<int>("RowNo") == 1
select myRow;

Drop vs Truncate vs Delete in SqlServer

Drop Command: If we want to destroy the existing tables present in the database we use the Drop Command.

DROP TABLE Students

Truncate Command: Removes all rows from a table. TRUNCATE TABLE is functionally the same as the DELETE statement with no WHERE clause specified.

TRUNCATE TABLE Students

The difference between Truncate and Delete is:

• Truncate table is faster in execution.


• Truncate will reset the identity function if present on the table to initial value again which will not happen in delete.

 

Url.Action vs Url.RouteUrl

Url.RouteUrl allows you to specify a particular route by name. This will force the usage of that route.

If you have multiple routes with similar parameters the Action method may pick a wrong one - it works based on the order of route definitions. This may take place when your routes have optional parameters.

Lazy loading/Deferred loading in Entity frame work

One of the important functions of Entity Framework is lazy loading. Lazy loading means delaying the loading of related data with its parent object, until you specifically request for it.

you can also turn off lazy loading for a particular property or an entire context. To turn off lazy loading for a particular property, do not make it virtual. To turn off lazy loading for all entities in the context, set its configuration property to false:

public partial class SchoolDBEntities : DbContext
{
    public SchoolDBEntities(): base("name=SchoolDBEntities")
    {
        this.Configuration.LazyLoadingEnabled = false;
    }
}

Below are the advantages of lazy loading:

• Minimizes start up time of the application.


• Application consumes less memory because of on-demand loading.


• Unnecessary database SQL execution is avoided.

The only one disadvantage is that the code becomes complicated. As we need to do checks if the loading is needed or not, there is a slight decrease in performance.

 

Events in the Global.asax file

The Global.asax file, also known as the ASP.NET application file, is an optional file that contains code for responding to application-level events raised by ASP.NET or by HttpModules and session-level events.

The following are some of the important events in the Global.asax file.

• Application_Init


• Application_Start


• Session_Start


• Application_BeginRequest


• Application_EndRequest


• Application_AuthenticateRequest


• Application_Error


• Session_End


• Application_End

The purpose of these event handlers is discussed in this section below.

Application_Init

The Application_Init event is fired when an application initializes the first time.

Application_Start

The Application_Start event is fired the first time when an application starts.

Session_Start

The Session_Start event is fired the first time when a user’s session is started. This typically contains for session initialization logic code.

Application_BeginRequest

The Application_BeginRequest event is fired each time a new request comes in.

Application_EndRequest

The Application_EndRequest event is fired when the application terminates.

Application_AuthenticateRequest

The Application_AuthenticateRequest event indicates that a request is ready to be authenticated. If you are using Forms Authentication, this event can be used to check for the user's roles and rights.

Application_Error

The Application_Error event is fired when an unhandled error occurs within the application.

Session_End

The Session_End Event is fired whenever a single user Session ends or times out.

Application_End

The Application_End event is last event of its kind that is fired when the application ends or times out. It typically contains application cleanup logic.

Application_Start/End events are called only once.

Encrypt ViewState info

View State:
The ViewState is used in retaining values between multiple requests for the same page. Viewstate is stored on page it self in encoded form. When an ASP.NET page is processed, the current state of the page and controls is hashed into a string and saved in the page as a hidden field. If the data is too long for a single field, then ASP.NET performs view state chunking (new in ASP.NET 2.0) to split it across multiple hidden fields. The following code sample demonstrates how view state adds data as a hidden form within a Web page’s HTML:

<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE” value="/wEPDwUKMTIxNDIyOTM0Mg9kFgICAw9kFgICAQ8PFgIeBFRleHQFEzQvNS8yMDA2IDE6Mzc6MTEgUE1kZGROWHn/rt75XF/pMGnqjqHlH66cdw==" />

The ViewState is stored in a hidden field with an ID __VIEWSTATE. This is nothing but a Base64 encoded string, and is not an encrypted string. So it can be easily decoded.

The main reasons for using Base64 encoding are as follows:

1. Base64 makes a string suitable for HTTP transfers


2. It makes it a little harder to read

But, after decoding the string (viewstate data), we can see the exact data that is stored inside the ViewState.

Solution

There are two different ways in which you can prevent someone from decrypting ViewState data.

1. You can make sure that the ViewState information is tamper-proof by using "hash codes". You can do this by adding EnableViewStateMAC=true in your page directive. MAC stands for "Message Authentication Code".

When we use EnableViewStateMac="True", during ViewState save, ASP.NET internally uses a hash code. This hash code is a cryptographically strong checksum. This is added with the ViewState content and stored in a hidden filed. During postback, the checksum data is verified again by ASP.NET. If there is a mismatch, the postback will be rejected.

2. The second option is to set ViewStateEncryptionMode="Always" with your page directives. This will encrypt the ViewState data.

ViewStateEncryptionMode has three different options that can be set:

• Always: encrypt the View State always.


• Auto: encrypt if a control requests for encryption. For this to happen, the control must call thePage.RegisterRequiresViewStateEncryption() method.


• Never: Never encrypt the ViewState.

<system.web>
<pages enableViewStateMac="true">
                viewStateEncryptionMode="Always">
</pages>
</system.web>