Multicast delegates in C Sharp (C#) - Time & Space Complexity

Time Complexity: Multicast delegates

O(n)

Understanding Time Complexity

When using multicast delegates, it's important to understand how the time to invoke all methods grows as more methods are added.

We want to know how the execution time changes when the delegate calls multiple methods.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

public delegate void Notify();

Notify notifyList = null;

notifyList += MethodA;
notifyList += MethodB;
notifyList += MethodC;

notifyList();

void MethodA() { /* do something */ }
void MethodB() { /* do something */ }
void MethodC() { /* do something */ }
    

This code creates a multicast delegate that calls three methods one after another.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Invoking each method in the delegate list one by one.
• How many times: Once per method added to the delegate.

How Execution Grows With Input

Each added method means one more call when the delegate is invoked.

Input Size (n)	Approx. Operations
3	3 method calls
10	10 method calls
100	100 method calls

Pattern observation: The total calls grow directly with the number of methods added.

Final Time Complexity

Time Complexity: O(n)

This means the time to invoke the delegate grows linearly with the number of methods it holds.

Common Mistake

[X] Wrong: "Invoking a multicast delegate takes constant time no matter how many methods it has."

[OK] Correct: Each method in the delegate list is called one after another, so more methods mean more calls and more time.

Interview Connect

Understanding how multicast delegates work helps you reason about event handling and callbacks, which are common in many programs.

Self-Check

"What if the delegate methods themselves call other delegates? How would that affect the overall time complexity?"