LINQ MinBy

Summary: in this tutorial, you will learn how to use the LINQ MinBy() method to find the element that has a minimum value based on a specified key selector function.

Introduction to the LINQ MinBy() method

The MinBy() method returns the minimum element in a sequence based on a specified key selector function.

Here’s the syntax of the MinBy() method:

TSource? MinBy<TSource,TKey> (
    this IEnumerable<TSource> source, 
    Func<TSource,TKey> keySelector
);Code language: C# (cs)

In this syntax:

• TSource is the type of element in the source sequence.
• TKey is a type of key used to compare the elements in the source sequence.
• source is an input sequence of values.
• keySelector is a function that extracts the key for each element.

The MinBy() method returns the element in the source sequence with the minimum key.

LINQ MinBy() method example

Suppose you have a Product class with three properties Name, Cost, and Price:

public class Product
{
    public string Name
    {
        get; set;
    }

    public decimal Price
    {
        get; set;
    }

    public decimal Cost
    {
        get; set;
    }

    public Product(string name, decimal cost, decimal price)
    {
        Name = name;
        Cost = cost;
        Price = price;
    }

    public override string ToString() => $"{Name}, Cost:{Cost}, Price:{Price}";
}Code language: C# (cs)

The following program uses the MinBy() method to find the product that has the lowest price:

using static System.Console;

var products = new List<Product>() {
    new Product("A",100,120),
    new Product("B",95,130),
    new Product("C",140,150),
};

var product = products.MinBy(p => p.Price);
WriteLine(product);Code language: C# (cs)

Output:

A, Cost:100, Price:120Code language: plaintext (plaintext)

In this example, we use the following selector function to instruct the MinBy() method to return the product with the lowest price:

p => p.PriceCode language: C# (cs)

To find the product with the lowest cost, you use the following selector function:

using static System.Console;

var products = new List<Product>() {
    new Product("A",100,120),
    new Product("B",95,130),
    new Product("C",140,150),
};

var product = products.MinBy(p => p.Cost);
WriteLine(product);Code language: C# (cs)

Output:

B, Cost:95, Price:130Code language: plaintext (plaintext)

Summary

• Use the LINQ MinBy() method to return the element in a sequence with the minimum key specified by a key selector function.