What is wrong with this example of inheritance?

Question

1.00/5 (3 votes)

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C#

private void button_Click(object sender, EventArg e)
{
	BirthdayParty partyOn = new BirthdayParty();
	
	MessageBox.Show( partyOn.getMessage("Shadid") );
	MessageBox.Show( partyOn.getPresent (8) );

	MessageBox.Show( partyOn.getParty( true) );
}

C#

Class HappyBirthday
{
    private string birthdayMessage;
    private string presentString;
    public HappyBirthday()
    {
        presentString = "Number of presents: ";
        birthdayMessage = "Happy Birthday";
}
public string getMessage(string givenName)
{
    return birthdayMessage + givenName;
}
public string getPresents(int numPresents)
{
    presentString = presentString + numPresents.ToString();
    return presentString;
}
}

C#

//====================================
//           A DERIVED CLASS
//====================================
class BirthdayParty : HappyBirthday
{
//=====================================================
//  DEFAULT CONSTRUCTOR CALLS THE base () CONSTRUCTOR
//=====================================================
public BirthdayParty() : base()
{
}
//=================
//      METHOD
//=================
public string getParty (bool haveParty)
{
    if (haveParty == true)
    return "Enjoy your party!";
    }
    else
    {
    return  "Sorry – No party for you!";
    }
}
}

Posted 3-Sep-14 2:39am

Member 9538830

Updated 3-Sep-14 2:59am

Herman<T>.Instance

v3

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Comments

ZurdoDev 3-Sep-14 8:53am

I give up. What is the problem with it?

Member 9538830 3-Sep-14 9:13am

Does not work. Reports an error. The example is from a book.

ZurdoDev 3-Sep-14 9:23am

And the error is?

Member 9538830 3-Sep-14 19:15pm

Errors:
//===============
// DERIVED CLASS
//===============
class BirthdayParty : HappyBirthday1 // Kakva je ovo greška???

Error 1 The type or namespace name 'HappyBirthday1' could not be found (are you missing a using directive or an assembly reference?)
………………………………………………………………………………………………………………………………………………………………….

private void button1_Click(object sender, EventArgs e)
.
.
.
MessageBox.Show( partyOn.getMessage("Shadid"));
MessageBox.Show(partyOn.getPresent(8));

Error 2 'BirthdayParty' does not contain a definition for 'getMessage' and no extension method 'getMessage' accepting a first argument of type 'BirthdayParty' could be found (are you missing a using directive or an assembly reference?)
Error 3 'BirthdayParty' does not contain a definition for 'getPresent' and no extension method 'getPresent' accepting a first argument of type 'BirthdayParty' could be found (are you missing a using directive or an assembly reference?)

ZurdoDev 3-Sep-14 20:38pm

That error won't come from the code you posted. The error is saying it does not know what HappyBirthday1 is. Note, you have a 1 on the end of HappyBirthday.

Member 9538830 4-Sep-14 4:49am

OK. Thank you. But, HappyBirthday1 is right name of the parent class, and BirthdayParty is the name of the class derived from HappyBirthday1. Why the next error is appeared: "BirthdayParty" does not contain a definition for "getMessage" etc ... if "BirthdayParty" is derived class from HappyBirthday1 class?

CPallini 3-Sep-14 8:53am

Why do you feel it is wrong?

Member 9538830 3-Sep-14 9:13am

Does not work. Reports an error. The example is from a book.

ClimerChinna 3-Sep-14 9:24am

have you tried solution1

Member 9538830 3-Sep-14 9:31am

Not yet, but I`ll try.

Member 9538830 3-Sep-14 19:13pm

I tried your solution and it works. But, your solution gives resultes in three separate message boxes. Could you change it so that all of three results are in one message box.

ClimerChinna 4-Sep-14 0:12am

change your button click event like below

private void button1_Click(object sender, EventArgs e)
{
BirthdayParty partyOn = new BirthdayParty();

MessageBox.Show( partyOn.getMessage("Shadid")+"\n"+partyOn.getPresents(8)+"\n"+partyOn.getParty( true));
}

Member 9538830 4-Sep-14 3:38am

Thank you very much ClimrChinna. I change it and solution works.

Although this may seem strange, but I still noticed a basic error (difference) that existed between the beginning of the program, and your solutions, that works.

Why "BirthdayParty" does not contain a definition for "getMessage" ... if BirthdayParty is derived class from HappyBirthday?

ClimerChinna 4-Sep-14 4:38am

The code which you have tried is correct as per logic, but your code is having small syntax errors like { missing, etc...

Member 9538830 3-Sep-14 19:18pm

These are errors:

//===============
// DERIVED CLASS
//===============
class BirthdayParty : HappyBirthday1 // Kakva je ovo greška???

Error 1 The type or namespace name 'HappyBirthday1' could not be found (are you missing a using directive or an assembly reference?)
………………………………………………………………………………………………………………………………………………………………….

private void button1_Click(object sender, EventArgs e)
.
.
.
MessageBox.Show( partyOn.getMessage("Shadid"));
MessageBox.Show(partyOn.getPresent(8));

Error 2 'BirthdayParty' does not contain a definition for 'getMessage' and no extension method 'getMessage' accepting a first argument of type 'BirthdayParty' could be found (are you missing a using directive or an assembly reference?)
Error 3 'BirthdayParty' does not contain a definition for 'getPresent' and no extension method 'getPresent' accepting a first argument of type 'BirthdayParty' could be found (are you missing a using directive or an assembly reference?)

[no name] 3-Sep-14 21:06pm

Your question is such a good example of the timewasting going on in this forum. The question is scatty and trivial. You show no evidence of having tried to solve it yourself. You provide no information. When a member takes their own time to look into and resolve your problem you don't bother to accept answer or thank them but ask for more free work on their part.

Member 9538830 4-Sep-14 3:27am

Thank you very much for your reply. Please bear in mind that I am a beginner and trying to learn how to use this forum.

If you look a little better, you're going to see that I thank the member who solved the problem and I accepted his solution.

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ClimerChinna · Accepted Answer · 2014-09-03T02:52:00

when you are asking a question, you need to post the error which you are getting with your code, so that we can solve it easily
any way i have posted my code which i have tested with your code

replace your code with below code

C#

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            BirthdayParty partyOn = new BirthdayParty();
	
	MessageBox.Show( partyOn.getMessage("Shadid"));
	MessageBox.Show( partyOn.getPresents(8) );
 
	MessageBox.Show( partyOn.getParty( true) );
        }
    }

    class HappyBirthday
{
    private string birthdayMessage;
    private string presentString;
    public HappyBirthday()
    {
        presentString = "Number of presents: ";
        birthdayMessage = "Happy Birthday";
}
public string getMessage(string givenName)
{
    return birthdayMessage + givenName;
}
public string getPresents(int numPresents)
{
    presentString = presentString + numPresents.ToString();
    return presentString;
}
}
 
 
//====================================
//           A DERIVED CLASS
//====================================
class BirthdayParty : HappyBirthday
{
//=====================================================
//  DEFAULT CONSTRUCTOR CALLS THE base () CONSTRUCTOR
//=====================================================
public BirthdayParty() : base()
{
}
//=================
//      METHOD
//=================
public string getParty (bool haveParty)
{
    if (haveParty == true)
    {
    return "Enjoy your party!";
    }
    else
    {
    return  "Sorry – No party for you!";
    }
}
}