[c#] LINQ Aggregate algorithm explained

In addition to all the great answers here already, I've also used it to walk an item through a series of transformation steps.

If a transformation is implemented as a Func<T,T>, you can add several transformations to a List<Func<T,T>> and use Aggregate to walk an instance of T through each step.

A more concrete example

You want to take a string value, and walk it through a series of text transformations that could be built programatically.

var transformationPipeLine = new List<Func<string, string>>();
transformationPipeLine.Add((input) => input.Trim());
transformationPipeLine.Add((input) => input.Substring(1));
transformationPipeLine.Add((input) => input.Substring(0, input.Length - 1));
transformationPipeLine.Add((input) => input.ToUpper());

var text = "    cat   ";
var output = transformationPipeLine.Aggregate(text, (input, transform)=> transform(input));
Console.WriteLine(output);

This will create a chain of transformations: Remove leading and trailing spaces -> remove first character -> remove last character -> convert to upper-case. Steps in this chain can be added, removed, or reordered as needed, to create whatever kind of transformation pipeline is required.

The end result of this specific pipeline, is that " cat " becomes "A".


This can become very powerful once you realize that T can be anything. This could be used for image transformations, like filters, using BitMap as an example;

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