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into (C# Reference)

Use the into contextual keyword to create a temporary identifier that stores the results of a group, join, or select clause. This identifier can act as a generator for additional query commands. When you use the new identifier in a group or select clause, it's sometimes called a continuation.

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The documentation identifies any feature first introduced in the last three versions of the language or in current public previews.

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The following example shows how to use the into keyword to create a temporary identifier named fruitGroup, which has an inferred type of IGrouping. By using this identifier, you can call the Count method on each group and select only those groups that contain two or more words.

class IntoSample1
{
    static void Main()
    {

        // Create a data source.
        string[] words = ["apples", "blueberries", "oranges", "bananas", "apricots"];

        // Create the query.
        var wordGroups1 =
            from w in words
            group w by w[0] into fruitGroup
            where fruitGroup.Count() >= 2
            select new { FirstLetter = fruitGroup.Key, Words = fruitGroup.Count() };

        // Execute the query. Note that we only iterate over the groups,
        // not the items in each group
        foreach (var item in wordGroups1)
        {
            Console.WriteLine($" {item.FirstLetter} has {item.Words} elements.");
        }
    }
}
/* Output:
   a has 2 elements.
   b has 2 elements.
*/

You only need to use into in a group clause when you want to perform additional query operations on each group. For more information, see group clause.

For an example of using into in a join clause, see join clause.

See also

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