Delegates and captured state

The idea

A delegate is a typed reference to callable behavior. Func<int,int> accepts an integer and returns an integer; Action<int> returns no value. Passing a transformation can remove duplicated loops while keeping the operation explicit. A delegate’s type describes its parameters and result, but does not promise that the body is pure or free of exceptions.

A lambda can capture local variables from its surrounding scope. It generally reads the captured variable’s current value when called, rather than a frozen value from creation time. This is useful for deliberate state but can surprise code that builds callbacks and invokes them later. If each callback should retain a different loop value, create a separate local copy in the loop body.

using System;
int offset = 2;
Func<int, int> shift = n => n + offset;
offset = 5;
Console.WriteLine(shift(3));

8

The lambda reads the updated captured offset when it executes.