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C# Average Method

Use the Average extension method from System.Linq on an IEnumerable.
Average. This is an extension method. It computes the average value using only one statement. Often we combine it with other LINQ methods.
Average notes. This method provides a declarative way to compute the average value of a sequence in the C# language. We can use Average with no argument, or pass in a lambda expression.Lambda
Example. First, add the "using System.Linq" directive to include the LINQ namespace. The Average method implementation is actually stored in the System.Core.dll file.LINQ

Tip: The Average method looks like an instance method when called, but it is not. It is an extension method.

Extension

Info: The program shows how to directly average the values in a double[] collection.

Note: Average is equivalent to adding up the total of all of the numbers, and then dividing that total by the number of elements.

C# program that computes averages using System; using System.Linq; class Program { static void Main() { // Use Average to compute average value. double[] array = { 1, 2, 3, 5, 0 }; double average = array.Average(); Console.WriteLine("AVERAGE: {0}", average); } } Output AVERAGE: 2.2
Overload, lambda. There are more overloads to Average. We can select the values we want to average from another collection with a selector delegate. We can pass a lambda expression.

Here: We use the Average method parameter to specify a function that will select a value from an existing sequence.

Tip: The lambda expression "x => x.Length" extracts the length of the strings and then averages those values.

String Length
C# program that uses Average with lambda using System; using System.Linq; class Program { static void Main() { // Use Average to compute average string length. string[] array = { "dog", "cat", "Codex" }; double average = array.Average(x => x.Length); Console.WriteLine("AVERAGE: {0}", average); } } Output AVERAGE: 3.66666666666667
Internals. How does Average() work? If you provide a selector parameter to Average, the method internally calls the Select extension method first.

Then: On that result, Average() checks the parameter for null, uses a foreach-loop, and divides the total value by the count.

NullForeach

Also: The Average extension method will throw an exception if it divides by zero.

Warning: Because of all the overhead in this method, this implementation will be slower than a for-loop approach.

For
A summary. You can use Average to compute the average value of a collection of numbers. And you can combine the Average extension with a Func selector. This will internally Select elements.Func
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