LINQ (Language Integrated Query) is a feature that allows querying collections and data sources using native C# syntax.

What is LINQ in C#? | FullStackPrep.Dev

💡 Concept: LINQ (Language Integrated Query)

LINQ is a feature in C# that introduces native syntax for querying collections and data sources directly within the language, improving readability and maintainability.

📘 Quick Intro

LINQ provides a unified model for querying diverse data sources like arrays, lists, XML, and databases using familiar query operators in C# syntax.

🧠 Analogy

Think of LINQ as a universal translator for data queries—it allows you to ask questions to any collection or database in a consistent language, no matter the source.

🔧 Technical Explanation

🔍 LINQ supports both query syntax and method syntax (fluent API).
⚙️ Enables filtering, projection, aggregation, grouping, and joining of data.
🎯 Provides strong typing and IntelliSense support.
🔄 Works on any IEnumerable<T> or IQueryable<T> data source.
🚀 Simplifies complex data manipulation operations in a declarative way.

🎯 Use Cases

✅ Querying collections like arrays, lists, and dictionaries.
✅ Filtering and transforming data easily.
✅ Working with XML and JSON data.
✅ Querying databases through LINQ to SQL or Entity Framework.

💻 Code Example

int[] numbers = {1, 2, 3, 4, 5, 6};
var evenNumbers = from num in numbers
                  where num % 2 == 0
                  select num;

foreach (var n in evenNumbers) {
    Console.WriteLine(n);
}
// Outputs 2, 4, 6

❓ Interview Q&A

Q1: What does LINQ stand for?
A: Language Integrated Query.

Q2: What are the two syntaxes used in LINQ?
A: Query syntax and method syntax.

Q3: Can LINQ query databases?
A: Yes, using LINQ to SQL or Entity Framework.

Q4: What interfaces does LINQ work with?
A: IEnumerable<T> and IQueryable<T>.

Q5: Can LINQ be used with XML?
A: Yes, LINQ to XML allows querying XML documents.

Q6: What advantage does LINQ provide?
A: Strongly-typed queries with IntelliSense support.

Q7: Can LINQ perform joins?
A: Yes, LINQ supports joins between data sources.

Q8: Does LINQ improve code readability?
A: Yes, it simplifies complex queries.

Q9: What is deferred execution in LINQ?
A: Query execution is delayed until the data is iterated.

Q10: Can LINQ be used for filtering data?
A: Yes, using where clauses.

📝 MCQs

Q1. What does LINQ stand for?

Language Independent Query
Local Integrated Query
Language Integrated Query
Linked IN Query

Q2. What are the two LINQ syntaxes?

Query and Method
Query and Lambda
Method and Lambda
Query and Select

Q3. Which interfaces does LINQ primarily work with?

ICollection
IEnumerable<T> and IQueryable<T>
IDisposable
IQueryable only

Q4. Can LINQ query XML data?

No
Yes
Only JSON
Only databases

Q5. What is deferred execution?

Immediate execution
Execution delayed until enumeration
Compile-time execution
Runtime optimization

Q6. Which LINQ clause is used to filter data?

from
select
where
join

Q7. Can LINQ perform joins?

No
Yes
Only with SQL
Only with databases

Q8. Does LINQ support strong typing?

No
Yes
Only with generics
No, dynamic only

Q9. What is the method syntax also known as?

Query syntax
Fluent syntax
Chain syntax
Method chaining

Q10. Is LINQ used for querying collections?

No
Yes
Only databases
Only files

💡 Bonus Insight

LINQ integrates querying capabilities directly into C# language, bridging the gap between programming and data manipulation, making your code more expressive, readable, and maintainable.

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What is LINQ in C#?