Can you list and explain the main methods of working with LINQ in C#?

The main LINQ methods in C# can be divided into several categories:

• Filtering:

  • Where — selects elements that satisfy a condition.

• Projection:

  • Select — transforms each element in the sequence.
  • SelectMany — projects each element into a collection and flattens the result.

• Sorting:

  • OrderBy, OrderByDescending — sort by a key.
  • ThenBy, ThenByDescending — perform additional sorting.

• Aggregation:

  • Count, Sum, Average, Min, Max — compute aggregate values.

• Joining:

  • Join — joins two sequences based on a key.
  • GroupJoin — groups elements from the second sequence.
  • Concat — concatenates two sequences.
  • Distinct — removes duplicates.

• Grouping:

  • GroupBy — groups elements by a key.

• Elements:

  • First, FirstOrDefault, Single, SingleOrDefault, Last, LastOrDefault — return elements based on a condition.

• Condition checks:

  • Any — checks if any elements satisfy a condition.
  • All — checks if all elements satisfy a condition.

Example of usage:

var numbers = new List<int> {1, 2, 3, 4, 5};
var evenSquares = numbers
    .Where(n => n % 2 == 0)
    .Select(n => n * n);

foreach(var num in evenSquares)
{
    Console.WriteLine(num); // Outputs 4 and 16
}

LINQ allows writing expressive and concise code for working with collections and data.