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

HTML Helper 

HTML Helper is just a method that returns a HTML string. The string can represent any type of content that you want.

For example, you can use HTML Helpers to render standard HTML tags like HTML <input>, <button> and <img> tags etc.
You can also create your own HTML Helpers to render more complex content such as a menu strip or an HTML table for displaying database data.





Example:


HtmlHelper.ActionLink @Html.ActionLink(“Create New”, ”Create”, ”Home”)

In the above example, @Html is an object of HtmlHelper class & ActionLink() is the extension method


Html is a property of type HtmlHelper included in base class of razor view WebViewPage


HtmlHelper class generates html elements For example, 

@Html.ActionList("Create New", "Create“, “Home”) would generate anchor tag <a href="/Home/Create">Create New</a>

HTML Element

TextBox @Html.TextBox("Textbox1", "val")

Output: <input id="Textbox1" name="Textbox1" type="text" value="val" />



TextArea @Html.TextArea("Textarea1", "val", 5, 15, null)

Output: <textarea cols="15" id="Textarea1" name="Textarea1" rows="5">val</textarea>

Password @Html.Password("Password1", "val")

Output: <input id="Password1" name="Password1" type="password" value="val" />


Hidden Field @Html.Hidden("Hidden1", "val")

Output: <input id="Hidden1" name="Hidden1" type="hidden" value="val" />


CheckBox @Html.CheckBox("Checkbox1", false)

Output: <input id="Checkbox1" name="Checkbox1" type="checkbox" value="true" /> <input name="myCheckbox" type="hidden" value="false" />


RadioButton @Html.RadioButton("Radiobutton1", "val", true)

Output: <input checked="checked" id="Radiobutton1" name="Radiobutton1" type="radio" value="val" />


Drop-down list @Html.DropDownList (“DropDownList1”, new SelectList(new [] {"Male", "Female"}))

Output: <select id="DropDownList1" name="DropDownList1"> <option>M</option> <option>F</option> </select>



Multiple-select Html.ListBox(“ListBox1”, new MultiSelectList(new [] {"Cricket", "Chess"}))

Output: <select id="ListBox1" multiple="multiple" name="ListBox1"> <option>Cricket</option> <option>Chess</option>

@Html.ActionLink("HomePage", Index.new{style='color:red');

Output: <a href="Index" style="color:red">HomePage</a>

@Html.DisplayName("Enter your username");

@HTMLDisplayNameFor(model => model.studentName);

The following table lists HtmlHelper methods and html control:


HtmlHelper - Html.ActionLink
Html Control - Anchor link

HtmlHelper - Html.ActionLinkFor
Html Control - Anchor link




HtmlHelper - Html.TextBox
Strogly Typed HtmlHelpers - Html.TextBoxFor
Html Control - Textbox



HtmlHelper - Html.TextArea
Strogly Typed HtmlHelpers - Html.TextAreaFor
Html Control - TextArea



HtmlHelper - Html.CheckBox
Strogly Typed HtmlHelpers - Html.CheckBoxFor
Html Control - Checkbox




HtmlHelper - Html.RadioButton
Strogly Typed HtmlHelpers - Html.RadioButtonFor
Html Control - Radio button




HtmlHelper - Html.DropDownList
Strogly Typed HtmlHelpers - Html.DropDownListFor
Html Control - Dropdown, combobox




HtmlHelper - Html.ListBox
Strogly Typed HtmlHelpers - Html.ListBoxFor
Html Control - Multi-select list box




HtmlHelper - Html.Hidden
Strogly Typed HtmlHelpers - Html.HiddenFor
Html Control - Hidden Field




HtmlHelper - Password
Strogly Typed HtmlHelpers - Html.PasswordFor
Html Control - Password textbox





HtmlHelper - Html.Display
Strogly Typed HtmlHelpers - Hmlt.DisplayFor
Html Control - Html text



HtmlHelper - Html.Label
Strogly Typed HtmlHelpers - Html.LabelFor
Html Control - Label



HtmlHelper - Html.DisplayName
Strogly Typed HtmlHelpers - Html.DisplayNameFor
Html Control - Display





HtmlHelper - Html.editory
Strogly Typed HtmlHelpers - Html.EditorFor
Html Control - Generates html controls based on data type of specified model property eg. textbox for string property numeric field for int, double or other numeric type.


 

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