LINQ Fundamentals in ASP.NET Core
💡 Concept Name
LINQ Fundamentals in ASP.NET Core
📘 Quick Intro
LINQ (Language Integrated Query) enables querying collections in a readable, expressive way using C#. It supports both in-memory collections and databases through LINQ to Objects and LINQ to Entities.
🧠 Analogy / Short Story
Imagine you're shopping in a supermarket. LINQ is like your shopping filter: "Give me all red fruits under ₹100 and sort them by name." LINQ allows you to write such filters in C# directly—clean and structured—just like organizing your shopping cart.
🔧 Technical Explanation
LINQ provides a unified way to query collections using operators like `Where`, `Select`, `OrderBy`, `GroupBy`, and `Join`. It has two syntaxes: Query Syntax (`from x in collection where ...`) and Method Syntax (`collection.Where(x => ...)`). LINQ queries can be applied to in-memory data (arrays, lists) or EF Core queries (IQueryable).
🎯 Purpose & Use Case
- ✅ Simplifies querying collections using C#
- ✅ Avoids verbose loops and conditional statements
- ✅ Integrates well with Entity Framework Core
- ✅ Supports transformation, filtering, grouping, and joining data
- ✅ Readable and composable code for business logic
💻 Real Code Example
var products = new List<Product>
{
new Product { Name = ""Apple"", Price = 80 },
new Product { Name = ""Mango"", Price = 120 },
new Product { Name = ""Banana"", Price = 40 }
};
// Get all products under ₹100 sorted by name
var cheapFruits = products
.Where(p => p.Price <= 100)
.OrderBy(p => p.Name)
.Select(p => p.Name);
foreach (var fruit in cheapFruits)
Console.WriteLine(fruit);
❓ Interview Q&A
Q1: What is LINQ?
A: A querying feature in C# to filter, sort, and project data using a readable syntax.
Q2: Name two LINQ syntaxes.
A: Query syntax and method syntax.
Q3: What is the return type of `Where()`?
A: `IEnumerable
Q4: What is the role of `Select()`?
A: It projects or transforms elements in a collection.
Q5: How does LINQ improve readability?
A: It uses declarative syntax instead of loops.
Q6: Can LINQ be used on databases?
A: Yes, via LINQ to Entities in EF Core.
Q7: What is deferred execution in LINQ?
A: Query execution happens when results are iterated, not when defined.
Q8: Can we chain multiple LINQ operations?
A: Yes, LINQ supports fluent chaining.
Q9: What is `FirstOrDefault()` used for?
A: Gets first matching element or null/default if none found.
Q10: Which LINQ operator is used for grouping?
A: `GroupBy()`
📝 MCQs
Q1. Which method filters a collection in LINQ?
- Select
- OrderBy
- Where
- GroupBy
Q2. Which LINQ syntax uses method chaining?
- Query Syntax
- Method Syntax
- SQL Syntax
- Lambda Syntax
Q3. What does `Select()` do?
- Filters data
- Deletes data
- Projects data
- Groups data
Q4. Which operator sorts elements?
- Where
- GroupBy
- OrderBy
- First
Q5. Which LINQ method checks for a condition match?
- All
- Count
- Any
- Sum
Q6. LINQ queries on EF Core produce:
- IEnumerable
- List
- IQueryable
- Array
Q7. Which LINQ method returns a single value?
- Select
- GroupBy
- First
- Single
Q8. `GroupBy()` is used to:
- Sort items
- Filter nulls
- Group items by key
- Paginate results
Q9. What does `Take(3)` do?
- Skips 3
- Sorts by 3
- Gets first 3 items
- Removes 3 items
Q10. Which LINQ method skips records?
- Skip
- Where
- Select
- Join
💡 Bonus Insight
LINQ not only works on collections and EF Core queries, but can also be used with XML (LINQ to XML), SQL (LINQ to SQL), and in-memory DataTables. Learning LINQ well boosts your productivity across nearly all data-heavy .NET applications.
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