juniorLINQ
What is GroupBy in LINQ?
Updated May 16, 2026
Short answer
GroupBy groups elements based on a key.
Deep explanation
It partitions data into groups where each group shares a common key.
Real-world example
Grouping customers by region.
Common mistakes
- Expecting sorted output from GroupBy.
Follow-up questions
- Is GroupBy deferred?
- Can groups be nested?