Home > Articles

Parameters and Methods

This chapter is from the book

This chapter is from the book

Declaring a Method

This section expands on the explanation of declaring a method to include parameters or a return type. Listing 5.4 contains examples of these concepts, and Output 5.1 shows the results.

Listing 5.4: Declaring a Method

public class IntroducingMethods
{
    public static void Main()
    {
        string firstName;
        string lastName;
        string fullName;
        string initials;
 
        Console.WriteLine("Hey you!");
 
        firstName = GetUserInput("Enter your first name: ");
        lastName = GetUserInput("Enter your last name: ");
 
        fullName = GetFullName(firstName, lastName);
        initials = GetInitials(firstName, lastName);
        DisplayGreeting(fullName, initials);
    }
 
    static string GetUserInput(string prompt)
    {
        Console.Write(prompt);
        return Console.ReadLine() ?? string.Empty;
    }
 
    static string GetFullName(  
          string firstName, string lastName) =>
              $"{ firstName } { lastName }";
 
 
    static void DisplayGreeting(string fullName, string initials)
    {
        Console.WriteLine(
            $"Hello { fullName }! Your initials are { initials }");
        return;
    }
 
    static string GetInitials(string firstName, string lastName)
    {
        return $"{ firstName[0] }. { lastName[0] }.";
    }
}

Output 5.1

Hey you!
Enter your first name: Inigo
Enter your last name: Montoya
Hello Inigo Montoya! Your initials are I. M.

Listing 5.4 declares five methods. From Main() the code calls GetUserInput(), followed by a call to GetFullName() and GetInitials(). All of the last three methods return a value and take arguments. In addition, the listing calls DisplayGreeting(), which doesn’t return any data.

Formal Parameter Declaration

Consider the declarations of the DisplayGreeting(), GetFullName(), and the GetInitials() methods. The text that appears between the parentheses of a method declaration is the formal parameter list. (As we will see when we discuss generics, methods may also have a type parameter list. When it is clear from the context which kind of parameters we are discussing, we simply refer to them as parameters in a parameter list.) Each parameter in the parameter list includes the type of the parameter along with the parameter name. A comma separates each parameter in the list.

Behaviorally, most parameters are virtually identical to local variables, and the naming convention of parameters follows accordingly. Therefore, parameter names use camelCase. Also, it is not possible to declare a local variable (a variable declared inside a method) with the same name as a parameter of the containing method, because this would create two local variables of the same name.

Method Return Type Declaration

In addition to GetUserInput(), GetFullName(), and the GetInitials() methods requiring parameters to be specified, each of these methods includes a method return type. You can tell that a method returns a value because a data type appears immediately before the method name in the method declaration. Each of these method examples specifies a string return type. Unlike parameters, of which there can be any number, only one method return type is allowable.

As with GetUserInput() and GetInitials(), methods with a return type almost always2 contain one or more return statements that return control to the caller. A return statement consists of the return keyword followed by an expression that computes the value the method is returning. For example, the GetInitials() method’s return statement is return $"{ firstName[0] }. { lastName[0] }.";. The expression (an interpolated string in this case) following the return keyword must be compatible with the stated return type of the method.

If a method has a return type, the block of statements that makes up the body of the method must not have an unreachable end point. That is, there must be no way for control to “fall off the end” of a method without returning a value. Often the easiest way to ensure that this condition is met is to make the last statement of the method a return statement. However, return statements can appear in locations other than at the end of a method implementation. For example, an if or switch statement in a method implementation could include a return statement within it; see Listing 5.5 for an example.

Listing 5.5: A return Statement before the End of a Method

public class Program
{
    // ...
 
    public static bool MyMethod()
    {
        string command = ObtainCommand();
        switch(command)
        {
            case "quit":
                return false;
            // ... omitted, other cases
            default:
                return true;
        }
    }
    // ...
}

(Note that a return statement transfers control out of the switch, so no break statement is required to prevent illegal fall-through in a switch section that ends with a return statement.)

In Listing 5.5, the last statement in the method is not a return statement; it is a switch statement. However, the compiler can deduce that every possible code path through the method results in a return, so that the end point of the method is not reachable. Thus, this method is legal even though it does not end with a return statement.

If particular code paths include unreachable statements following the return, the compiler will issue a warning that indicates the additional statements will never execute.

Though C# allows a method to have multiple return statements, code is generally more readable and easier to maintain if there is a single exit location rather than having multiple returns sprinkled through various code paths of the method.

Specifying void as a return type indicates that there is no return value from the method. As a result, a call to the method may not be assigned to a variable or used as a parameter type at the call site. A void method call may be used only as a statement. Furthermore, within the body of the method the return statement becomes optional, and when it is specified, there must be no value following the return keyword. For example, the return of Main() in Listing 5.4 is void, and there is no return statement within the method. However, DisplayGreeting() includes an (optional) return statement that is not followed by any returned result.

Although, technically, a method can have only one return type, the return type could be a tuple. As a result, starting with C# 7.0, it is possible to return multiple values packaged as a tuple using C# tuple syntax. For example, you could declare a GetName() method, as shown in Listing 5.6.

Listing 5.6: Returning Multiple Values Using a Tuple

public class Program
{
    static string GetUserInput(string prompt)
    {
        Console.Write(prompt);
        return Console.ReadLine() ?? string.Empty;
    }
    static (string First, string Last) GetName()                                            
    {
        string firstName, lastName;
        firstName = GetUserInput("Enter your first name: ");
        lastName = GetUserInput("Enter your last name: ");
        return (firstName, lastName);
    }
    static public void Main()
    {
        (string First, string Last) name = GetName();                                       
        Console.WriteLine($"Hello { name.First } { name.Last }!");
    }
}

Technically, we are still returning only one data type, a ValueTuple<string, string>. However, effectively, you can return any (preferably reasonable) number you like using each item within the tuple.

Expression Bodied Methods

To support the simplest of method declarations without the formality of a method body, C# 6.0 introduced expression bodied methods, which are declared using an expression rather than a full method body. Listing 5.4’s GetFullName() method provides an example of the expression bodied method:

static string GetFullName( string firstName, string lastName) =>

In place of the curly brackets typical of a method body, an expression bodied method uses the “goes to” operator (fully introduced in Chapter 13), for which the resulting data type must match the return type of the method. In other words, even though there is no explicit return statement in the expression bodied method implementation, it is still necessary that the return type from the expression match the method declaration’s return type.

Expression bodied methods are syntactic shortcuts to the fuller method body declaration. As such, their use should be limited to the simplest of method implementations—generally expressible on a single line.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020