Calculate average of values in a List in C#

This post will discuss how to calculate the average of values in a List in C#.

The Enumerable.Average method is the shortest and most idiomatic way to compute the average of a sequence of numeric values. The following code example shows invocation for this method:

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> numbers = new List<int> { 1, 4, 6, 8 };

double average = numbers.Average();

Console.WriteLine("The average is {0}", average);

}

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Output:

The average is 4.75

The Enumerable.Average method throws System.InvalidOperationException if the source sequence is empty. You can easily handle the exception as follows.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<int> numbers = new List<int> { 1, 4, 6, 8 };

double average = numbers.Count > 0 ? numbers.Average() : 0.0;

Console.WriteLine("The average is {0}", average);

}

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Output:

The average is 4.75

The Enumerable.Average method has an overload that takes a transform function to apply to each element. It can be used to compute an average of some specific field from a list of objects, as demonstrated below:

using System;

using System.Linq;

using System.Collections.Generic;

public class Person

{

public string name { get; set; }

public int age { get; set; }

public Person(string name, int age)

{

this.name = name;

this.age = age;

}

public override string ToString() {

return "[" + name + ", " + age + "]";

}

public class Example

{

public static void Main()

{

List<Person> persons = new List<Person> {

new Person("x", 27), new Person("y", 20),

new Person("z", 24), new Person("z", 30)

};

double average = persons.Count > 0 ? persons.Average(item => item.age) : 0.0;

Console.WriteLine("The average is {0}", average);

}

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Output:

The average is 25.25

The transform function can also be invoked on each element of the input sequence of String values to compute the average.

using System;

using System.Linq;

using System.Collections.Generic;

public class Example

{

public static void Main()

{

List<string> numbers = new List<string> { "1", "4", "6", "8" };

double average = numbers.Average(num => int.Parse(num));

Console.WriteLine("The average is {0}", average);

}

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Output:

The average is 4.75

That’s all about calculating the average of values in a List in C#.

Calculate average of values in a List in C#

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