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Quantifier operations in LINQ (C#)

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Quantifier operations return a Boolean value that indicates whether some or all of the elements in a sequence satisfy a condition.

The following illustration depicts two different quantifier operations on two different source sequences. The first operation asks if any of the elements are the character 'A'. The second operation asks if all the elements are the character 'A'. Both methods return true in this example.

LINQ Quantifier Operations

The standard query operator methods that perform quantifier operations are listed in the following section.

Methods

Method Name Description C# Query Expression Syntax More Information
All Determines whether all the elements in a sequence satisfy a condition. Not applicable. Enumerable.All
Queryable.All
Any Determines whether any elements in a sequence satisfy a condition. Not applicable. Enumerable.Any
Queryable.Any
Contains Determines whether a sequence contains a specified element. Not applicable. Enumerable.Contains
Queryable.Contains

Query Expression Syntax Examples

All

The following example uses the All to check that all strings are of a specific length.

class Market
{
    public string Name { get; set; }
    public string[] Items { get; set; }
}

public static void Example()
{
    List<Market> markets = new List<Market>
    {
        new Market { Name = "Emily's", Items = new string[] { "kiwi", "cheery", "banana" } },
        new Market { Name = "Kim's", Items = new string[] { "melon", "mango", "olive" } },
        new Market { Name = "Adam's", Items = new string[] { "kiwi", "apple", "orange" } },
    };

    // Determine which market have all fruit names length equal to 5
    IEnumerable<string> names = from market in markets
                                where market.Items.All(item => item.Length == 5)
                                select market.Name;

    foreach (string name in names)
    {
        Console.WriteLine($"{name} market");
    }

    // This code produces the following output:
    //
    // Kim's market
}

Any

The following example uses the Any to check that any strings are start with 'o'.

class Market
{
    public string Name { get; set; }
    public string[] Items { get; set; }
}

public static void Example()
{
    List<Market> markets = new List<Market>
    {
        new Market { Name = "Emily's", Items = new string[] { "kiwi", "cheery", "banana" } },
        new Market { Name = "Kim's", Items = new string[] { "melon", "mango", "olive" } },
        new Market { Name = "Adam's", Items = new string[] { "kiwi", "apple", "orange" } },
    };

    // Determine which market have any fruit names start with 'o'
    IEnumerable<string> names = from market in markets
                                where market.Items.Any(item => item.StartsWith("o"))
                                select market.Name;

    foreach (string name in names)
    {
        Console.WriteLine($"{name} market");
    }

    // This code produces the following output:
    //
    // Kim's market
    // Adam's market
}

Contains

The following example uses the Contains to check an array have a specific element.

class Market
{
    public string Name { get; set; }
    public string[] Items { get; set; }
}

public static void Example()
{
    List<Market> markets = new List<Market>
    {
        new Market { Name = "Emily's", Items = new string[] { "kiwi", "cheery", "banana" } },
        new Market { Name = "Kim's", Items = new string[] { "melon", "mango", "olive" } },
        new Market { Name = "Adam's", Items = new string[] { "kiwi", "apple", "orange" } },
    };

    // Determine which market contains fruit names equal 'kiwi'
    IEnumerable<string> names = from market in markets
                                where market.Items.Contains("kiwi")
                                select market.Name;

    foreach (string name in names)
    {
        Console.WriteLine($"{name} market");
    }

    // This code produces the following output:
    //
    // Emily's market
    // Adam's market
}

See also