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What is the difference between Select and SelectMany in LINQ?`

ICSM Computer 525 24 Jun 2025

Ask by ICSM Computer

Updated 24 Jun 2025

1 Answers

ICSM Computer 24 Jun 2025

Answer:

Select: Projects each item into a result. Returns a collection of collections when used on nested data.
SelectMany: Flattens a nested collection.

var list = new[] {
    new { Name = "John", Hobbies = new[] { "Chess", "Coding" } },
    new { Name = "Jane", Hobbies = new[] { "Running", "Reading" } }
};

var select = list.Select(x => x.Hobbies);     // IEnumerable<string[]>
var selectMany = list.SelectMany(x => x.Hobbies); // IEnumerable<string>

Use SelectMany to flatten lists (e.g., inner joins, sub-collections).

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