• What are LINQ aggregate functions ? Give examples (e.g., Count , Sum , Average , Min , Max ).

  • Explain the difference between Single() and SingleOrDefault(). What happens if the sequence contains more than one matching element? Mid-Level

  • Explain the difference between First() and FirstOrDefault() . When might using FirstOrDefault() lead to unexpected null reference exceptions if not handled carefully?

  • What is the difference betweenSelectandSelectMany? Provide a use case forSelectMany.

  • How do you perform joins ( inner , group , left outer ) between collections or data sources using LINQ ?

  • Explain how theGroupBy operatorworks inLINQ. Provide an example. Mid Level

  • How do you perform sorting in LINQ ? Explain OrderBy , OrderByDescending , ThenBy , and ThenByDescending .

  • What is projection in LINQ?

  • Explain the purpose and usage of the Select extension method/clause.

  • Can you explain the purpose and usage of the Where extension method/clause?

  • Explain the difference between expression lambdas and statement lambdas .

  • What are lambda expressions in C , and how are they used in LINQ method syntax ?

  • How does LINQ work with differentdata sourceslikein-memory collections( LINQ to Objects ),SQL databases( LINQ to SQL/Entities ), andXML( LINQ to XML )?

  • What is the difference betweenIEnumerableandIQueryablein the context of LINQ ? When should you use each?

  • What are the advantages of using deferred execution ?

  • Which LINQ methods cause immediate execution? Give examples.

  • Explain the concept ofdeferred executioninLINQ. How does it differ fromimmediate execution?

  • What are the three main components of a standard LINQ query operation?

  • Explain the difference betweenLINQ query syntaxandmethod syntaxinC. When would you prefer one over the other?

  • What isLINQ(Language-Integrated Query) and what problem does it solve?