LINQ Interview Questions and Answers

Last updated on Feb 06, 2023
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LINQ Interview Questions

LINQ is an abbreviated form of Language -integrated Quer. It is an innovation that is used to bridge the gap between two platforms, namely Visual Studio 2008 and the .NET framework. There is a number of LINQ queries that are used to retrieve data from the data sources. In this, blog, we are providing a collection of LINQ interview questions that will help you in cracking interviews. Traditionally, the queries against data can be expressed in the form of simple strings without supporting IntelliSense. Likewise, users can use the coding patterns for the purpose of transforming data in XML documents, ADO.NET datasets, .NET collections, SQL databases and another format for which LINQ provider is available. We are providing a vast collection of LINQ interview questions, which will help you in achieving success factors.

Most Frequently Asked LINQ Interview Questions

Here in this article, we will be listing frequently asked LINQ Interview Questions and Answers with the belief that they will be helpful for you to gain higher marks. Also, to let you know that this article has been written under the guidance of industry professionals and covered all the current competencies.

Q1. What is Select() and SelectMany() in LINQ?

In LINQ, Select() and SelectMany() are projection operators. The use of a Select() operator is to select a value from a collection whereas the use of SelectMany() operator is to select values from a group of collection, i.e. a nested collection.


public class PhoneNumber
    public string Number { get; set; }
public class Person
   public IEnumerable PhoneNumbers { get; set; }
   public string Name { get; set; }
IEnumerable people = new List();
IEnumerable> phoneLists = people.Select(p => p.PhoneNumbers);
IEnumerable phoneNumbers = people.SelectMany(p => p.PhoneNumbers);
var directory = people .SelectMany(p => p.PhoneNumbers,
(parent, child) => new { parent.Name, child.Number });

Q2. What is the best way for retrieving single record in LINQ?

Use the First() or FirstOrDefault() command to retrieve single row records in LINQ.


var users = (from u in dc.Users where u.UserName == usn select u).FirstOrDefault();

Q3. What is the difference between Linq and lambda expression?

Following are the difference between LINQ expression and LAMBDA expression

LINQ expression Lambda expression
In order to extend the functionality a query capabilities LINQ expression to the language syntax of C# and Visual Basic. It is a function that is used to create expressions in the form of a tree. With the help of lambda expression, users can write local functions that can be passed as a return value of function calls
Q4. What is the difference between Single() and First() extension methods in LINQ?
Single() First()
Used to return a single specific element of a query or a default value if no result is found. It is used to return the first element of any query with multiple values.
Used when exactly one element is expected as a result. Used when there are multiple result expectations but you only need the first value.
Q5. What are the types of LINQ?
LINQ is of five types namely-
  • LINQ to objects
  • LINQ to dataset
  • LINQ to entities
Q6. What is Query and Sequence operators in LINQ?

The query is an expression which is used to recover data from a variety of data sources and query can be expressed in specialized languages.

Three types of actions can be performed on LINQ query namely
  • Get data source
  • Create Query
  • Execution of Query
LINQ does not support sequence operators but it is having the following qualities-
  • Take lambda expression with an index parameter
  • Depend on the properties of sequential rows
  • Depend on the CLR implementation
Q7. What is Action in LINQ?

Action in LINQ is a delegate type that is used to declare delegate variables without any need to define a custom type. The Action types that represent delegate without return value are the Action types in the System namespace

Q8. How LINQ is beneficial than stored procedures?

LINQ is beneficial than stored procedure due to-

  • Debugging
  • Type safety
  • Deployment
Q9. What is the difference between SkipWhile() and Skip() methods in LINQ?
Skip() SkipWhile()
Used to specify the amount (number) of items to skip in a LINQ expression. Used to supply a predicate function on how many numbers to skip.
It will take an integer argument and then simply skips those n numbers from the top of the given IEnumerable It works on a per-line basis. It shall continue to skip if the value returned from the function is true.
Syntax: yourlist.Skip(5) Syntax: yourList.SkipWhile(x => x.marks < 50)
Q10. What is expression trees in LINQ?

In LINQ, an Expression tree is nothing but expressions systematically organized in a tree-like data structure. Here, each node in an expression tree relates to expression. This is just like an in-memory representation of a lambda expression in which only the actual elements of the query are held and not the result of the query.

Advantages of LINQ
  • Unified data access (Single syntax to learn)
  • Strongly typed (During completion automatically catch errors)
  • IntelliSense (Prompt attributes and syntax)
  • Bind-able result sets
  • Allows debugging through the .NET debugger
  • Type checking at compile time
Disadvantages of LINQ
  • Not suitable to write complex queries like SQL
  • It does not support SQL features such as cached execution
  • Performance degraded if the query is incorrect
  • In order to incorporate changes in query, you need to recompile and redeploy it

The LINQ interview questions that most probably asked during the interview are providing in this blog that will help you in order to achieve the desired goals.

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