Delegates

Learn how delegates let you treat methods as values that can be passed around and invoked dynamically.

What is a Delegate?

A delegate is a type-safe reference to a method — it lets you treat a method like a value: store it in a variable, pass it as a parameter, or return it from another method.

Declaring and Using a Delegate

delegate int MathOperation(int a, int b);

static int Add(int a, int b) => a + b;
static int Multiply(int a, int b) => a * b;

MathOperation operation = Add;
Console.WriteLine(operation(3, 4)); // 7

operation = Multiply;
Console.WriteLine(operation(3, 4)); // 12

Output

Click Run to see what this code prints.

Built-in Delegate Types

Rather than declaring a custom delegate every time, C# provides built-in generic delegate types for common cases.

Type	Purpose
Action	A method with no return value
Action<T>	A method with parameters and no return value
Func<T, TResult>	A method that takes T and returns TResult
Predicate<T>	A method that takes T and returns bool

Func<int, int, int> add = (a, b) => a + b;
Console.WriteLine(add(5, 3));

Action<string> log = message => Console.WriteLine($"LOG: {message}");
log("Application started");

Output

Click Run to see what this code prints.

FAQs

When would I use a delegate in real code?

Delegates power events (next lesson), LINQ, and any API that lets you "plug in" custom logic — like sorting with a custom comparison.

Summary

A delegate is a type-safe reference to a method.
Func, Action, and Predicate are built-in generic delegate types.
Delegates are the foundation events and LINQ are built on.

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