Create Web API for CRUD operation

So ladies and gentlemen here we will create a new web application project in which GET, POST, PUT, and delete method will be used for CRUD operation.
 
So first we make one, for this you have to go to the file --> New --> Project then write on name section (whatever you want) and without disturbing the rest, you just clicked on the OK button.

 
and then you choose to MVC option in next tab and same as it as click on OK button.

So, as you can see this our project empty project is ready to launch on localhost...let's run first before write any code.
 

For this, Shortcut command press by keyboard


ctrl + F5

As you can see this here are displaying the project in browser by localhost

URL http://localhost:59322/

Add Models

So before proceeding here on the left side you are able to see some options, with the help of which we will create controller class, model class.
 

Wait, if your Solution Explorer not showing there, don't worry...follow to our steps.

Click on view --> Click Solution Explorer, Server Explorer option etc.

First we will create class and for this you have go to Models option and right click on this and go to Add --> class --> choose first option (Class) --> change the class name like in our case (class name is Student) and then click Add. button.

 

After creating a class then we write some code for generating a table name or attribute name like StudentID, StudentName

In Student.cs file -


So, write this command in your code...as it as same and don't forget to add LINE no 5 code (System.ComponentModel.DataAnnotations;)

[Key]
public int StudentID { get; set; }
public string StudentName { get; set; }

NOTE - The get method returns the value of the variable name . The set method assigns a value to the name variable. The value keyword represents the value we assign to the property.
 

Then go to IdentityModels.cs file write this command also.
 

public DbSet <Student> Student { get; set; }

Save all file (ctrl + s).
 

Before diving into long sea..let's build first and create a migrations, add migrations and update-database.


For this Click on Build --> Build Solution
 

Then,

Go to Tools --> NuGet Package Manager --> Package Manager Console
 

enable-migrations 

And at the same time you are able to see that the file is being created inside the migrations.
 

add-migration init 

update-database

• The Enable-Migration command creates the Migrations folder, which contains a script to initialize the database. 
•  
  
• (init is a migration name)
•  
• Update the database for any kind of changes

Now, after updating the database as you can see this in Server explorer section

Data connection --> Tables --> Table name (in our case Students is table name).

 

Add Web API Controller

So before proceeding here on the left side you are able to see some options, with the help of which we will create controller class, model class.

For create a Controller class right click on controller --> Add --> choose Controller option.
 

 

Choose MVC 5 Controller - Empty and then click on Add button.

This will open Add Scaffold popup as shown below.

 

Attention Please in Add Controller popup tab, here Controller name is DefaultController. So, Remove "Default" word and type any name whatever you want (in our case we are going to write "Student") then click on Add button.

 


In StudentController.cs file write some code for doing a CRUD operation... but first we are doing a Create operation.

Type this command -

[HttpPost]
public ActionResult Create(Student s)
        {
         ApplicationDbContext db = new ApplicationDbContext();
         db.Student.Add(s);
         db.SaveChanges();
         return View();
        }

If in case any error are there like this shown below, then tension we are here for your help.

Simple mouse click on this red line error and as you can see that A yellow light bulb appear here so click on little arrow and choose "using WebApplication2.Models; (In your case this name may be different, don't worry)

Hurray Error is gone :-) :-p


and "using WebApplication2.Models;" line is added on StudentController.cs file. DONE

Hurray Error is gone :-) :-p

and "using WebApplication2.Models;" line is added on StudentController.cs file. DONE
 

Now, we will create a Add view. So, for this you have to right click on "Create" --> Add view --> and choose the correct all option as it as same.

then Click on Add button.

This will open Add Scaffold popup as shown below.

In solution explorer, there are appear Create.cshtml file.

and finally we will run.

ctrl + F5

or

Click on Middle top side Green color button...click on it.

public ActionResult Display()
        {
            ApplicationDbContext db = new ApplicationDbContext();
            var lst = db.Student.ToList();
            return View(lst);
        }
        public ActionResult Details(int id)
        {
            ApplicationDbContext db = new ApplicationDbContext();
            var s = db.Student.Where(x => x.StudentID == id).SingleOrDefault();
            return View(s);
        }

Please Be Patience We Will Update Very Soon :-)

Disclaimer

All tutorials are for informational and educational purposes only and have been made using our own routers, servers, websites and other vulnerable free resources. we do not contain any illegal activity. We believe that ethical hacking, information security and cyber security should be familiar subjects to anyone using digital information and computers. Hacking Truth is against misuse of the information and we strongly suggest against it. Please regard the word hacking as ethical hacking or penetration testing every time this word is used. We do not promote, encourage, support or excite any illegal activity or hacking.

What is CRUD?

CRUD is stands for "Create, Read, Update, and Delete".

These are the four basic operation for managing data in an application.

In HTTP we find four main methods that can perform processing on data that are defined in the REST architecture. This correspondence can also be done with CRUD.


GET     ->  Retrieve
POST    ->  Create
PUT     ->  Update
Delete  ->  Delete

CRUD Operation

To Insert

Public class HomeController: Controller 

[HTTPPOST]

//controller is a class

public ActionResult InsertData(Students s)
 {
   ApplicationDb db = new ApplicationDb();
   
   db.Students.Add(s);
   db.SaveChanges();
   
   return view();
   
  }
  

To read

ApplicationDb db = new ApplicationDb();

var lst = db.Students.ToList();

List<Students> list = db.students.ToList();

foreach(var obj in list)
{
console.writeline (obj.StudentsId);
console.writeline (obj.StudentsName);
}

To Update

ApplicationDb db = new ApplicationDb();

Students s = db.Students.Where(x => x.StudentsId == items.StudentsId).SingleOrDefault();

//items is a model name

s.StudentsName = new StudentsName;

db.SaveChanges();
 

To Edit Single Update

Public Class HomeController: Controller

{

ApplicationDb db = new ApplicationDb();

Students s = db.Students.Where(x => x.StudentsId == StudentsId).SingleOrDefault();

return view(s);

}

To Delete

List <Students> s = db.studentsToList()


if(s!=null)
{
  foreach(var t in s)
   {  
     db.students.remove(t);
   }
  
  db.savechanges();
 
} 

Disclaimer

All tutorials are for informational and educational purposes only and have been made using our own routers, servers, websites and other vulnerable free resources. we do not contain any illegal activity. We believe that ethical hacking, information security and cyber security should be familiar subjects to anyone using digital information and computers. Hacking Truth is against misuse of the information and we strongly suggest against it. Please regard the word hacking as ethical hacking or penetration testing every time this word is used. We do not promote, encourage, support or excite any illegal activity or hacking.

LINQ expression

The Linq important part of Linq is about getting sequences from data sources. By default, the data sources that can be requested by Linq are:

Object (Linq to Objetcs)
XML fragments or docs (Linq to XML)
ADO.Net DataSet (Linq to DataSet)
SQL Server (Linq to SQL)
Entity Framework (Linq to Entities


LINQ is a unified programming model for any kind of data.



var result = from s in stringList
             where s.Contains("Tutorials")
             select s;
             

result = result variable
s = Now property of stringList  transfer in s (range variable)
strList = Sequence | Queryable collection
Contains = Conditional Expression
Where and Select = Standard Query Operators             

• From s in student select  s.studentid, s.studentname;

• From s in student select  s.studentid == 10;

Q) Display all the students whose roll no is 15

In SQL - Select * From Where

In LINQ - From s in student select Rollno = 15;

Simple Where clause

var query_where1 = from a in AccountSet
        where a.Name.Contains("Atul")
        select a;

Multiple Select and where operator

Example: Multiple Select and where Operator

var studentNames = studentList.Where(s => s.Age > 18)
                              .Select(s => s)
                              .Where(st => st.StandardID > 0)
                              .Select(s => s.StudentName);





Example: LINQ Query returns Collection of Anonymous Objects


var teenStudentsName = from s in studentList
                       where s.age > 12 && s.age < 20
                       select new { StudentName = s.StudentName };
                       
                       
                       

 

                       

Q) List out the three main components of LINQ? Explain what is the extension of the file, when LINQ to SQL is used?

Three main components of LINQ are

    Standard Query Operators
    Language Extensions
    LINQ Providers

The extension of the file used is .dbml




Q) What are the types of LINQ?

    LINQ to Objects
    LINQ to XML
    LINQ to Dataset
    LINQ to SQL
    LINQ to Entities
    
    

Q) What are Anonymous Types?


Anonymous types are types that are generated by compiler at run time. When we create a anonymous type we do not specify a name. We just write properties names and their values. Compiler at runtime create these properties and assign values to them.



var k = new { FirstProperty = "value1", SecondProperty = "value2" };
Console.WriteLine(k.FirstProperty);



Q) What is Anonymous function?

An Anonymous function is a special function which does not have any name. We just define their parameters and define the code into the curly braces.

Q) Define what is let clause?

In a query expression, it is sometimes useful to store the result of a sub-expression in order to use it in subsequent clauses. You can do this with the let keyword, which creates a new range variable and initializes it with the result of the expression you supply.

LinQ Operators

Filtering Operators - Where
                 - OfType


Filtering is an operation to restrict the result set such that it has only selected elements satisfying a particular condition.

Disclaimer