Into keyword

The into keyword is used in a select or group clause to create a temporary identifier that stores a query.
Use this when you must perform additional query operations on a query after a grouping or select operation:

// percentileQuery is an IEnumerable<IGrouping<int, Country>>
var percentileQuery =
    from country in countries
    let percentile = (int)country.Population / 10_000_000 // Group according to population in ranges of 10M.
    group country by percentile into countryGroup  // countryGroup is the temporary identifier.
    where countryGroup.Key >= 20 // Additional query operations.
    orderby countryGroup.Key
    select countryGroup;