LINQ Interview Questions

Introduction

The term "Language-integrated Queer" is referred to as "LINQ." It is a breakthrough that enables the communication between Visual Studio 2008 and the .NET framework, two different platforms. Data is retrieved from the data sources using a variety of LINQ queries. We've compiled a list of LINQ interview questions and their answers in this blog post to assist you in excelling in interviews.

So, let’s get started with the LINQ interview questions.

Top LINQ Interview Questions and Answers For 2024

1. What is LINQ?

Language Integrated Query is known by the acronym LINQ. It is a module for the.NET framework that links native data querying features to the.net Language. It provides simple data access from in-memory objects, databases, XML documents, and many more sources.

2. What are the benefits of LINQ in Dataset?

LINQ has the following advantages:

• LINQ is mainly used to extract complicated queries from datasets.
• Values from two separate data sets are combined using LINQ.
• Additionally, a unique value from the data collection is fetched using it.
• Compared to a SQL query, LINQ offers a more precise method of dataset querying.
• LINQ provides more features than ADO.NET.

3. What is the LINQ architecture?

LINQ has a three-layered architecture. The language extensions are located in the top layer, and the data sources are located in the bottom layer. The objects used as the data sources often implement the general IEnumerable or IQueryable interfaces.

Other than the fundamental LINQ query and data sources, an additional element is presently called the LINQ provider. The purpose of a LINQ provider is to translate a LINQ query into a format that the available data sources can understand.
 

4. What are the different forms of writing LINQ query syntax?

A LINQ query to data sources can be written in one of two ways.

1. Expression syntax or query syntax
2. Method Extension Syntax or Method Syntax

5. Explain the Query syntax?

The query syntax is comparable to the database's Structured Query Language. The C# or VB code contains a description of it.

Syntax:

from <range variable> in <IEnumerable<T> or IQueryable<T> Collection>
<specific Query Operators> <lambda expression>
<select or groupBy operator> <result formation>

 The key components of query syntax are listed below.

• It begins with the keyword FROM and concludes with the keyword SELECT or GROUP BY.
• The syntax resembles that of SQL (Structured Query Language).
• To create the desired output, it employs a variety of operators, including joining, grouping, sorting, and filtering operators.
• It uses implicitly typed variables to store the LINQ query's outcome.

6. What is LINQ method syntax?

Some additional Enumerable or Queryable static class methods are used in the LINQ method syntax. Because it makes it possible to invoke several extension methods, LINQ Method Syntax is also known as fluent syntax. The LINQ query result can be stored in an implicitly typed variable.

Syntax:

// Collection of String  
IList<string> stringList = new List<string> () {   
                                     "Python Developer",  
            ".Net Developer",  
            "Web Developer",  
            "Full Stack Developer" ,  
            "Python"};  
// Syntax of LINQ Query  
var result = stringList.  
Where(s => s.Contains("Coding"));

7. What is LINQ to XML?

The built-in document reform features of the DOM (Document Object Model) are provided by LINQ to XML, which also supports LINQ Queries. It allows us to edit an XML document's query, navigate, and save changes. It enables us to create questions to search through and retrieve a set of elements and attributes. It resembles XPath and XQuery quite a little.
 

8. Describe LINQ to SQL.

One of the ADO.NET technologies is LINQ to SQL. The relational data is managed by it as an object. The language-integrated queries in the object are converted to SQL via LINQ and sent to the database for processing. When the database responds, LINQ to SQL converts the responses back to objects.

9. What are the different types of LINQ?

It is important to know the various types of LINQ used as it is often asked in LINQ interview questions. Following is a list of the various types of LINQ

• LINQ to Objects
• LINQ to Entities
• LINQ to DataSet
• LINQ to SQL (DLINQ)
• LINQ to XML(XLINQ).

In addition to the types of LINQ mentioned above, there is also one called PLINQ, which is Microsoft's parallel LINQ.

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10. Explain is a LinqDataSource control.

LinqDataSource is a vital dataset component if you use LINQ in an ASP.NET webpage. It controls, retrieves, and alters data and sets the properties in the markup text. Additionally, it can explicitly tie data sources to other ASP.NET controls on a page. It is comparable to ObjectDataSource controls, and SQL Datasource controls in this way.
 

11. What makes LINQ and stored procedures different?

The following list highlights some key distinctions between LINQ and stored procedures often asked in the LINQ interviews:

• Because stored procedures adhere to a correct (Expected) execution plan.
• Unlike a stored procedure, a SQL query is simpler to avoid runtime mistakes.
• In contrast to stored procedures, which do not support debugging, LINQ does.
• In comparison to stored procedures, LINQ supports a variety of databases.
• LINQ-based solutions are easier to install than stored procedure-based solutions.

12. What is API in LINQ?

Classes that implement the IEnumerable or IQueryable interfaces can implement LINQ queries. The System.Linq namespace  System provides several classes. Linq namespace that offers the interfaces needed for LINQ queries.

LINQ queries use some extension methods for classes that implement the IEnumerable or IQueryable interfaces.

Must Read IEnumerable vs IQueryable.
 

13. In LINQ, what is an Expression Tree?

Expression Tree construction makes extensive use of lambda expressions. Each node serves as an impression in an Expression Tree, which displays code in a tree-like structure. Expression trees may be compiled into code and executed.

Through the API, the.NET framework's Expression class is utilized to generate expression trees. Assignment and a few control flow expressions, including conditional blocks, loops, and try-catch blocks, are also supported by the Expression Trees API. We may produce expression trees that are more intricate by using the API as opposed to lambda expressions.
 

14. What is LINQ Lambda expression?

LINQ refers to a function with no name as a lambda expression. The syntax is expanded by being made concise and precise. Despite not being as readable as a LINQ query, it is just as significant. Lambda expression has a constrained range. It is not reusable.

Syntax:

(Input Variable) => Method Expression  

The type is chosen during compilation via a lambda expression. We enclose a parameter as an input on the left side of the expression with a bracket (). Any name may be used for the parameter. To transmit a parameter from the left to the right side, use the equal to (=) symbol before the parameter name, followed by the greater one (>) sign. The needed procedure is carried out on the right side utilizing the input password given by the left side parameter. Lambda expression is the name of the full syntax.
 

15. What is the fundamental syntax for a LINQ query in Visual Basic?

The basic LINQ query syntax in Visual Basic is started with the From keyword and finishes with the Select or Group By keyword. Other keywords, such as Where, Order By, Order By Descending, etc., can be used to carry out extra tasks, such as data filtering or data generation in a particular order.
 

16. What is the fundamental syntax for a LINQ query in C#?

The fundamental syntax in C# begins with the from keyword and ends with the Select or Group By keyword. Another clause, such as Where, Order By, Order By Descending, etc., can be used. For carrying out tasks like data filtering or data generation in a particular order.
 

17. What does the term "DataContext class" mean? How does it connect to LINQ?

The DataContext class serves as a passing point for the LINQ to SQL framework. It serves as the basis for every access mapped over a database connection.

A Data context can be made easily and effectively. Empty DataContext classes prepared for configuration are represented as a blank design surface after adding LINQ to SQL classes. The DataContext class contains details on database connection methods. It also alters the data in the database. DataContext classes are given access to the connection data provided by the first item for configuration.
 

18. Why does the FROM clause occur before the SELECT clause in LINQ?

When LINQ is used with other programming languages besides C#, all variables must first be defined. The LINQ query's "FROM" clause specifies the parameters or criteria for choosing records. Thus, with LINQ, the FROM clause must come before the SELECT.

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19. Explain the PLINQ?

It is one of the most commonly asked LINQ interview questions. Parallel LINQ is referred to as PLINQ. It is a LINQ to object parallel implementation. Due to its tight ties to the task parallel library, it supports parallel programming. With some queries, it makes it easier to use many processors automatically. PLINQ can speed up LINQ to Objects queries by effectively utilizing all of the host computer's cores.
 

20. What are the standard LINQ query operators?

LINQ query operators are often an interviewer’s favorite in the LINQ interview questions, so it is important to prepare them thoroughly

The methods that make up the LINQ pattern are the standard query operators. These methods are used on sequences and objects that implement the IEnumerableT> or the IQueryableT> interfaces. Filtering, projection, sorting, aggregation, and other query features are available through the basic query operators.

There are two groups of LINQ standard query operators. The first group works with IEnumerable<T> type objects, whereas the second group works with IQueryable<T> type objects.

Take a look at the following syntax:

var voter= from v in voterList where v.age>18 select v;  

In the example above, the operators where and select are standard query operators. 
 

21. List some important Standard Query Operators used in LINQ.

Another most frequently asked LINQ interview question. Based on their functionality, the LINQ standard query operators can be divided into groups based on their functionality.

22. What are the primary LINQ components, please? In the case of LINQ to SQL, what is the file extension?

There are three primary elements to LINQ:

• LINQ Providers
• Language Extensions,
• Standard Query Operators.

When using LINQ to SQL, the file extension is .dbml.
 

23. What do Anonymous Types mean? Discuss its limitations.

An anonymous type is one that the compiler creates at runtime. When constructing the Anonymous compiler, the name is not required, but we may still define the names of the properties and their values. The compiler creates these attributes, and runtime values are assigned to them. In LINQ queries, the anonymous class is helpful. While running queries, it saves the interim result.

Additionally, there are several limitations for Anonymous types:

• Anonymous types cannot implement interfaces.
• No methods can be specified for anonymous types.
• The static members cannot be defined.
• It is required to initialize all defined properties.
• We are limited to defining public fields.

24. Describe LINQ compiled queries.

There can be an incident where we need to run a specific query repeatedly. With LINQ, we can build a query and have it always be compiled.

Advantages of Compiled Queries:

• Since these queries don't need to be compiled every time, they execute quickly.
• These queries can be used as often as needed after being created once.
• Even if a query's parameter changes, these queries must be recompiled.

Example:

static class MyCompliedQueries {
    public static Func <DataClasses1DataContext, IQueryable <Person>> CompliedQueryForPerson =
        CompiledQuery. Compile((DataClasses1DataContext context) = >from c in context. Persons select c);
}

25. Give the differences between the extension methods Skip() and SkipWhile().

26. How do LINQ's Single() and First() extension functions vary?

27. What distinguishes N-layer architecture from N-tier architecture?