11.2. Method Signatures and Calls

11.2.1. Method Signatures

When you decide to create your own method, there is a standard syntax that C# requires in order to run your method when you call it. This syntax is the template for your method signature.

Access Modifier [static modifier] Return Type MethodName(Parameter List)
{
   Method Body
}

  • Access Modifier: This determines visibilty of methods between classes, and whether or not it can instanciate new objects. Since our methods in this chapter are limited to the MainClass we will leave them off.

  • Static Modifier: If your method is static, you must include this between your access modifier and return type. Else this is ommitted.

  • Return Type: If the method is returning a value, this indicates what data type it will be. Not all methods return values. Methods that do not return a value have a return type of void.

  • Method Name: The method’s unique identifier. This is what you use to call your method.

  • Parameter List: A parameter is a placeholder for specific data that the method will act upon. Paraemeters are optional. In these cases the () are still part of the method call, but remain empty.

  • Method Body: This is where you code your method. Note it is contained between {}.

11.2.2. Creating a Method

Using our template, let’s build a simple method.

Example

static int SquareTheNumber(int num)
{
   return num * num;
}

In this example, we are skipping the access modifier. The reason for this is that we are working within a single class. If we had multiple classes this would be more significant. We will discuss this more when we get to class and class members.

We are using the static modifier. This lets C# know that this method belongs to the current class it is contained in and not to expect anything new to be created.

Our return type is int. This lets you know how to use the method. If you were expecting a double then you will need to modify your return type.

SquareTheNumber is the method name. Notice that it is all in PascalCase where all words are capitalized and spaces removed.

SquareTheNumber has a single parameter, int num, which is a placeholder that tells you what input is expected along with the data type. In this example, SquareTheNumber is expecting one input of type int. The input is labeled num to provide you more context on what to expect or how to use the method.

When writing your own methods, provide as many clues as possible to help with readability. The method body shows you how the input will be manipulated within the method. Here it will be used to square itself. This method will return a value which we can use elsewhere in our code. Since this method is static, we can treat anything returned as a regular value. This means you can store the method as a variable, pass the method into expressions or other methods, or print it.

To sum up the method SquareTheNumber: use with an int value and the method will return the squared value.

11.2.2.1. Method Calls

A few notes about the Main method before we move on. The Main method is where you call methods. You build methods outside of the Main method.

Let’s walk through an example about placement for building your method and calling your method with the SquareTheNumber method.

Example

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using System;

class MainClass {

   static int SquareTheNumber(int num)
   {
      return num * num;
   }

   public static void Main (string[] args) {

      int digit = 4;
      int squaredNum = SquareTheNumber(digit);
      int squaredAndSummed = squaredNum + SquareTheNumber(digit);

      Console.WriteLine(squaredNum);
      Console.WriteLine(squaredAndSummed);
      Console.WriteLine(SquareTheNumber(5));

   }
}

repl.it

Console Output

16
32
25

You should be fairly familiar with the replit IDE by now.

  • Line 1 is where the using statement goes.

  • Line3 introduces the MainClass. The MainClass starts at Line 3 and ends at Line 21

  • Starting at Line 11 is the Main method statement. The Main method is contained between Lines 11-20 within the MainClass.

The purpose of the Main method is to exectue your program. This is where you call or invoke the methods you create. You cannot build your methods inside the Main method. They must be built outside the Main method but inside your MainClass.

In this example, we placed our SquareTheNumber method between Lines 5-8. This makes it inside the MainClass but outside the Main method.

11.2.3. Invoking the Method

We are using static methods with expected returns, these take input and return output, or values. So we must provide them with input if we want to see them work. Since this method is returning a numeric value, it needs to be stored somewhere. You can create a variable to do so, as we did in Line 13 with the variable squaredNum.

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int digit = 4;
int squaredNum = SquareTheNumber(digit);

Console.WriteLine(squaredNum);

Output

16

If you notice in Line 13 we also invoked the method with the input variable digit from Line 12. When we print squaredNum we see the result 16, as expected since 4 * 4 is 16.

Another way to take advantage of the returned value in this static method is to use the method call as part of an expression. This is what we did in Line 14.

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int digit = 4;
int squaredNum = SquareTheNumber(digit);
int squaredAndSummed = squaredNum + SquareTheNumber(digit);

Console.WriteLine(squaredAndSummed);

Output

32

And the last example in Line 18 is to use an integer literal or place the required data type value in the parentheses. In this example, we called SquareTheNumber and passed 5 directly in the parentheses. When we printed the results, we got 25, as expected.

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Console.WriteLine(squaredNum(5));

Output

25

These are three ways to invoke, or call, static methods that have a return type. Return types are not required. Methods that return nothing are called void methods. When working with void methods, the call is a slightly different. We will look at them next.

Method invocation or invoking the method are synonmous terms for calling the method.

11.2.4. Check Your Understanding

Question

What is the expected output returned by the Doubles method if the input, x, was 7?

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static int Doubles(int x)
{
   return (2 * x);
}

  1. 14

  2. 49

  3. 77

  4. 7