C# Anonymous Methods – Inline Delegates Made Simple

Introduction – Why Use Anonymous Methods in C#?

In modern C# programming, especially in event-driven or delegate-based code, sometimes you need a quick way to define logic without naming the method. This is where anonymous methods shine. They provide a way to create inline methods without declaring them separately—ideal for one-time-use actions and reducing code clutter.

In this guide, you’ll learn:

• What anonymous methods are in C#
• Syntax and usage with delegates and events
• Comparison with lambda expressions
• Real-world use cases and best practices

Core Concept – What Is an Anonymous Method?

An anonymous method is a method without a name, defined using the delegate keyword, and assigned to a delegate variable or passed directly as a delegate parameter.

Syntax:

delegate(int x, int y)
{
    return x + y;
};

Code Example – Anonymous Method with Delegate

delegate void Greet(string name);

Greet greetUser = delegate(string name)
{
    Console.WriteLine($"Hello, {name}!");
};

greetUser("Alice");

Output:

Hello, Alice!

Explanation:

• delegate(string name) { ... } defines an anonymous method.
• It’s assigned directly to a delegate variable (greetUser).
• Called like a normal method.

Anonymous Methods vs Named Methods

Anonymous Method with Event Handling

button.Click += delegate(object sender, EventArgs e)
{
    Console.WriteLine("Button clicked!");
};

Use Case: Event handling in Windows Forms or WPF without writing a separate handler method.

Anonymous Method with Return Value

delegate int Square(int num);

Square sq = delegate(int x)
{
    return x * x;
};

Console.WriteLine(sq(5)); // Output: 25

Use Case: Return-based logic inside delegates.

Anonymous Method vs Lambda Expression

// Anonymous Method
delegate(string msg)
{
    Console.WriteLine(msg);
};

// Lambda Expression (preferred)
msg => Console.WriteLine(msg);

Best Practice: Prefer lambda expressions for shorter, cleaner syntax in modern C#.

Limitations of Anonymous Methods

• Cannot access ref or out parameters from outer scope.
• Less concise than lambda expressions.
• Cannot be used with async directly (use lambdas instead).

Best Practices & Tips

Tip: Use anonymous methods only when needed—for quick logic inside delegates or events.

Pitfall: Don’t overuse; if logic is long or reused, create a named method.

Best Practice: Replace anonymous methods with lambda expressions (=>) in C# 3.0+ for cleaner syntax.

Real-World Use Cases

• Event handlers in UI frameworks (WinForms, WPF)
• Passing quick logic to LINQ methods (though lambda is preferred)
• ️ Timer callbacks or background worker actions
• Inline sorting/comparison logic

Summary – Recap & Next Steps

Key Takeaways:

• Anonymous methods let you define inline delegates without names.
• Ideal for one-off event handlers or small delegate-based logic.
• Prefer lambda expressions in modern C# for conciseness.

Real-world relevance: Useful in UI event programming, threading callbacks, and legacy LINQ applications.

FAQ Section

What is the difference between an anonymous method and a lambda expression in C#?
Anonymous methods use delegate syntax, while lambda expressions use =>. Lambdas are more concise and preferred.

Can anonymous methods have parameters?
Yes, they can define and accept parameters just like regular methods.

Can I use async in anonymous methods?
No. Use lambda expressions for async logic.

When should I use an anonymous method over a named method?
Use anonymous methods when logic is short, single-use, and tied closely to an event or delegate.

Are anonymous methods still used today?
Rarely. Since C# 3.0, lambda expressions are more commonly used due to cleaner syntax.