How Does LINQ's Aggregate Function Work?

LINQ Aggregate: The Ins and Outs in a Nutshell

Often overlooked, the Aggregate function in LINQ is a powerful tool that deserves better illumination. Let's explore its essence in a clear and concise manner.

Aggregate performs sequential operations on each element of a list, where each operation considers the results of preceding operations. In other words, it starts by operating on the first and second elements, then carries the result forward.

Example 1: Summing Numbers

Consider an array of numbers: [1, 2, 3, 4].

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

Aggregate will calculate the sum: (1 2) 3 4 = 10. It adds subsequent elements to the running total, resulting in the final sum.

Example 2: Concatenating Strings

Next, let's 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

In this case, Aggregate combines each character with a comma, resulting in the concatenated string.

Example 3: Multiplying Numbers with a Seed

Aggregate also offers an overload that accepts a seed value:

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

Starting with the seed value of 5, Aggregate multiplies each element of the array with it, resulting in the cumulative product: ((5 10) 20) 30 40 = 1200000.

In summary, Aggregate allows you to perform sequential operations on elements in a list, where each operation builds upon the preceding results. It's a versatile function that can be utilized to solve various data manipulation problems.

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