How Does LINQ's Aggregate Function Work: A Step-by-Step Explanation?

LINQ Aggregate Demystified: A Step-by-Step Guide

LINQ's Aggregate function can often be a source of confusion. In this article, we will delve into the inner workings of Aggregate and provide clear and concise explanations with real-world examples.

Understanding Aggregate

Aggregate is an operation that iterates over a sequence of elements, applying a specified function (lambda expression) to each element and the previously accumulated result. It essentially performs consecutive operations on the elements, carrying the intermediate results forward.

Example 1: Summing Numbers

Let's start with a simple example of summing a list of numbers:

var nums = new[] { 1, 2, 3, 4 };
var sum = nums.Aggregate((a, b) => a + b);
Console.WriteLine(sum); // Output: 10

In this example, the Aggregate function initializes a result with the first element (1). It then applies the lambda expression (a b) to the current result (1) and the next element (2), resulting in 3. This process continues, adding each element to the previous result.

Example 2: Creating a CSV from Strings

Aggregate can also be used for string manipulation. Here's how you can create a comma-separated string from an array of characters:

var chars = new[] { "a", "b", "c", "d" };
var csv = chars.Aggregate((a, b) => a + "," + b);
Console.WriteLine(csv); // Output: a,b,c,d

Example 3: Multiplying Numbers with a Seed

Aggregate supports an overload that takes an initial seed value to kickstart the calculations. Consider the following example:

var multipliers = new[] { 10, 20, 30, 40 };
var multiplied = multipliers.Aggregate(5, (a, b) => a * b);
Console.WriteLine(multiplied); // Output: 1200000

In this case, the aggregate operation starts with the seed value (5) and applies the multiplication lambda expression (a * b). Each element of the sequence is multiplied by the previous result and carried forward, producing the final result of 1200000.

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