<figure><img alt="" src="https://cdn-images-1.medium.com/max/1024/0*7PLF5_fdmmyDnaEU" /><figcaption>Photo by <a href="https://unsplash.com/@efekurnaz?utm_source=medium&amp;utm_medium=referral">Efe Kurnaz</a> on <a href="https://unsplash.com?utm_source=medium&amp;utm_medium=referral">Unsplash</a></figcaption></figure>It could be confusing to differentiate between the two major delegate types in C# — Func and Action, due to their similar syntax and parent type. While both delegate types could receive arrow functions or method group values, the difference lies in what they are expected (or not expected) to return. Func methods are expected to return a value while Action methods are expected to be void.In this article, we would explore the differences between the two delegate types as well as appropriate use-cases.To understand the two types, we need to first understand what a delegate is and how it is intended to be used.<h3>What are Delegates in C#</h3>Delegates (simply put) help us assign methods to variables. As such, a delegate could be used to pass a method as a parameter to other methods.For the sake of <a href="https://www.freecodecamp.org/news/orthogonality-in-software-engineering/#:~:text=Orthogonality%20is%20a%20software%20design,a%20term%20borrowed%20from%20mathematics.">orthogonality</a>, we sometimes have the need to pass a method, based on some criteria to an executing method to invoke — and that’s where delegates come in.Delegates can be declared at namespace-level. They are also used for callbacks. It is also possible to have either arrow functions or class methods assigned to a delegate. There is also support for chaining delegate callbacks, provided they have the same signatures.Declaring a delegate is similar to declaring a class in C#. Take this for example.<pre>public class DelegateExample { public delegate string Greet(); public DelegateExample() { Greet greet = this.SayHelloWorld; greet(); } private string SayHelloWorld() { return &quot;Hello world&quot;; } }</pre><h3>Func in C#</h3>The last type parameter in a Func declaration is the type of the output value. As we know, a Func must return a value. So, we must always have at least one type parameter.Let’s see a simple example of a Func in C#.<pre>public class FuncExampleOne { Func&lt;string&gt; Greet; public FuncExampleOne() { Greet = this.GreetUserInEnglish; Greet(); } public string GreetUserInEnglish() { return &quot;Hello! How are do you today&quot;; } }</pre>In the example above, we have a method GreetUserInEnglish which returns a string. We then assign it to a Func&lt;string&gt; variable, which we later invoke right before exiting the constructor.Let’s take another example of a Func, taking a number parameter and returning a string output.<pre>public class FuncExampleTwo { Func&lt;int, string&gt; SayTemperature; public FuncExampleTwo() { SayTemperature = this.GiveTemperatureSummary; Console.WriteLine(SayTemperature(30)); } public string GiveTemperatureSummary(int temp) { return $&quot;It's {temp} degrees outside.&quot;; } }</pre>A Func variable could also be an arrow function and we could pass a Func variable as a parameter to other methods, as we see the example below.<pre>public class FuncExampleThree { public FuncExampleThree() { Func&lt;int, string&gt; GetFriendlyTemp = (int temp) =&gt; { return $&quot;It's {temp} degrees outside.&quot;; }; DisplayTempText(GetFriendlyTemp); // It's 30 degrees outside. } public void DisplayTempText(Func&lt;int, string&gt; getFriendlyTemp) { Console.WriteLine(getFriendlyTemp()); } }</pre><h3>Action in C#</h3>Most of the convention of Func variables also apply to Action. The major difference being that an Action does not return anything. As such, all the type parameters of any Action declaration are of input parameters. In the case where the Action does not accept any parameter, no type parameter is required.For example, this would be a valid Action declaration in C#.<pre>public class ActionExampleOne { Action Greet; public DelegateExample() { Greet = this.SayHelloWorld; Greet(); } public void SayHelloWorld() { Console.WriteLine(&quot;Hello world!&quot;); } }</pre>From the signature of an Action, we can tell that they’ll be perfect for callbacks.Another feature unique to Action variables, is the ability to chain them. We could chain Action variables, so long as they have the same signatures. In this case, the methods will be invoked in the order they were chained.<pre>public class ActionChainExample { public ActionChainExample() { Action&lt;int&gt; GetFriendlyTemp = (int _) =&gt; { }; GetFriendlyTemp += (int temp) =&gt; { Console.Write($&quot;It's {temp} degrees outside.&quot;); }; GetFriendlyTemp += (int temp) =&gt; { string _season = temp &lt; 40 ? &quot;winter&quot; : &quot;summer&quot;; Console.Write($&quot; We are in {_season} season!&quot;); }; GetFriendlyTemp(45); // It's 45 degrees outside. We are in summer season! } }</pre><h3>Conclusion</h3>When having to choose between both delegate types, ask yourself the following questionsWhat does this method return? If it returns nothing, use an Action. If you have an async method or a method that returns anything, use a Func.Would I have a need to chain this method? If you would have a need to chain this method, an Action would work better than a Func.Thanks for reading! 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Learn the difference between two major delegate types in C# — Func and Action.

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C# Delegates: Difference between Func and Action

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