Linq interview question.

1. What is LINQ in c#? Why LINQ is required?

LINQ or language integrated query is the collection of standard query operators which provides query facility in .net framework language like c#, vb.net.

LINQ acts as bridge between real world of data and world of objects.

2. What are the types of LINQ?

•  LINQ to objects
• LINQ to xml
• LINQ to dataset
• LINQ to LINQ
• LINQ to entity

3. Why LINQ is useful than stored procedure?

Debugging: - We can debug LINQ because it the part of .net. Visual studio debugger can be used to debug LINQ. But we cannot debug stored procedure.

Deployment: - for stored procedure, additional script is required but for LINQ everything get compiled into single DLL hence deployment becomes easy.

Type Safety: - LINQ is type safe, so query will give error at compile time.

4. What are main components of LINQ? Explain what is the extension of file when LINQ to Sql is used?

The main components of LINQ are

• Standard Query Operator
• Language Extension
• LINQ Provider

Extension of file used in LINQ to sql is .dbml.

5. Define what is Where clause and Let clause?

Where clause: - Allows adding some conditional filters to LINQ query.

Let clause: - It allows defining variable and assigning it a value calculated from the data value.

 6. Why SELECT clause comes after FROM clause in LINQ?

With other programming languages and c#, it requires declaring all variables first. “FROM” clause of LINQ query define the range or condition to select records. So FROM clause must appear before SELECT clause.

7. What is lambda expression in LINQ?

A lambda expression is an anonymous function that you can use to create delegate or expression tree types. By using lambda expressions, you can write local functions that can be passed as arguments or return as the value of function call. Lambda expressions are particularly helpful for writing LINQ query expression.

Example: -

Lambda expression x=> x*x specifies a parameter that’s named x and return the value of x squared.

8. Different between Skip and Skipwhile in LINQ?

• Skip: - It is taking integer argument and from the given IEnumerable it skip the top n numbers.
• Skipwhile: - It will continue to skip the element as far as the input condition is true. It will return all the remaining element if the condition is false.

9. what is the role of DataContext classes in LINQ?

DataContext acts as a bridge between Sql Server Database and LINQ to Sql. For accessing the data from database and changing data from database , it conatains connection string and function.