What is the problem of inheritance in program?

Question

Why does the compiler give error about my inheritance that student form doesn't have constructor.

Please,Guide me.

class Student:Person

{
public int Student_Number;
public string Field;
public int Average;
public int Student_ID;

public void student(int Student_Number, string Field, int Average,int Student_ID)
{
this.Student_Number = Student_Number;
this.Field = Field;
this.Average = Average;
this.Student_ID = Student_ID;
}

Ranjit Powar · Answer

You need to change the Solution Platform from "Any CPU" to "x86". The steps are given below 1. Right Click on the Solution File in Solution Explorer 2. Click on the Configuration Manager. 3.Click on the Active Platform Drop down, If x86 is already there then select that, else Click on New 4.Select x86 from the new platform dropdown 5.Compile and Run your application,

Vulpes · Answer

Yes, you can. In fact, if you don't, then the above code won't work because the Student constructor is now calling the Person class constructor which takes 4 parameters.

Vulpes · Answer

Your Student class begins with an upper case letter but your constructor student begins with a lower case letter. As C# is case sensitive, the two need to match exactly.

Vulpes · Answer

You haven't posted the code for the Person class but suppose it looks like this: class Person { public string Name; public Person(string name); { Name = name; } } Then you'll get a compiler error because it doesn't contain a constructor which takes no parameters. If that's the reason for the error, then this would solve it: class Person { public string Name; public Person(string name); { Name = name; } public Person() { } }

Vulpes · Answer

I can't see any other error in the code you've posted but, if the Person class doesn't have a constructor which takes no parameters, then you'll get a compiler error because the Student constructor calls its base class constructor implicitly. If that's not the reason for the error, then can you tell us what the error is and post the relevant code.

Vulpes · Answer

This code is working OK for me: using System; class Person { public string Name; public string LastName; public int ID_Number; public int Age; public string properties { get { return string.Format(Name+" "+ LastName + " " + Age + " " + ID_Number.ToString()); } } public Person(String Name, String LastName, int Age, int ID_Number) { this.Name = Name; this.LastName = LastName; this.Age = Age; this.ID_Number = ID_Number; } } class Student: Person { public int Student_Number; public string Field; public int Average; public int Student_ID; public Student(int Student_Number, string Field, int Average,int Student_ID, string Name, string LastName, int Age, int ID_Number) : base (Name, LastName, Age, ID_Number) { this.Student_Number = Student_Number; this.Field = Field; this.Average = Average; this.Student_ID = Student_ID; } } class Program { static void Main() { Student s = new Student(123, "Computing", 72, 262, "Fred", "Bloggs", 20, 117356); Console.Write("{0} {1} {2} {3} ", s.Student_Number, s.Field, s.Average, s.Student_ID); Console.WriteLine(s.properties); Console.ReadKey(); } } The output is: 123 Computing 72 262 Fred Bloggs 20 117356

Ranjit Powar · Answer

Either add constructor with no parameters in Person class or pass parameters to existing constructor from Student class constructor.

Vulpes · Answer

The problem is what I suspected - the Person class doesn't have a constructor which takes no parameters. So, if you add this constructor to your Person class, the error should go away: public Person() { }

Vulpes · Answer

The point is that the Person class must contain a constructor which takes no parameters. It can also contain other constructors which do take parameters. If this isn't the reason for the error then, as Ranjit says, post your code.

Joe Wilson · Answer

Thank you for your answer.

Joe Wilson · Answer

Please tell me how can i pass parameters to existing constructor from Student class constructor. The answer which has been sent by Vulpes wasn't correct.

Joe Wilson · Answer

Unfortunately your answer wasn't correct i think please check it again.

Joe Wilson · Answer

I mean i want to use an administration form which request user to enter username and password and after check them with information of database let user to enter to the main form. Please guide me to solve my problem or give me a sample about my question.

Ranjit Powar · Answer

What do you mean?

Joe Wilson · Answer

Could you please help me use an special code to confirm database information in order to enter to the main form?

Joe Wilson · Answer

Thank you very much for your answer, by the way how can I use an special form to confirm the information of Access data base please guide me to use code in confirmation form.

Joe Wilson · Answer

So,if i use this code i can use parameters in person class ,too,can't I?

Joe Wilson · Answer

As Ranjit said How can i pass parameters to existing constructor from Student class constructor?

Joe Wilson · Answer

Yes,But i have another problem too, I use this code in other windows form in order to confirm my data base information to enter to the form 1 but compiler don't compile this part of my program. What should i do? My Code: private void Acceptbtn_Click(object sender, EventArgs e) { Connection.connectionString = @"provider = microsoft.Ace.oledb.12.0; Data source = D:\Database 10.accdb"; Connection d1 = new Connection(); bool b = d1.IsExist("select * from Administration where Student_Number = '" + textBox3.Text + "' and Student_ID = '" + textBox2.Text + "'"); if (b) { this.Hide(); Form1 m1 = new Form1(); m1.ShowDialog(); } else lblInfo.Text = "Not Exist !"; }

Ranjit Powar · Answer

Is your problem is solved?

Joe Wilson · Answer

Thank you very Much

Joe Wilson · Answer

Thank you for your answer,by the way what is this problem how can i solve that? problem: When i use display button to show the database information in data grid view so the below error appear,How can i solve? An unhandled exception of type 'System.InvalidOperationException' occurred in System.Data.dll Additional information: The 'microsoft.Ace.oledb.12.0' provider is not registered on the local machine.

Joe Wilson · Answer

It is my class constructor that i used in my program and i have used this code in other program but there isn't problem in that by the way the version of NET FRAMEWORK that i had used was 4 but i use 4.5 currently. class Person { public string Name; public string Last Name; public int ID_Number; public int Age; public string properties{get {return string.Format(Name+" "+Last Name+" "+Age+" "+ID_Number.ToString());} } public Person(String Name, String LastName, int Age ,int ID_Number) { this.Name = Name; this.LastName = LastName; this.Age = Age; this.ID_Number = ID_Number; } }

Joe Wilson · Answer

OK I will send you my code.

Ranjit Powar · Answer

Hey, post all your code.

Joe Wilson · Answer

Do you think it must contain parameters in constructor ?

Joe Wilson · Answer

No could you please guide me?

Joe Wilson · Answer

?

Joe Wilson · Answer

I have used constructor in person class too, So what is the problem?

Ranjit Powar · Answer

how do you create object of student class?

Joe Wilson · Answer

I did that but compiler gave me another mistake. Please Guide me.

Vulpes · Answer

In this case, you can't because the parameters you're passing to the Student constructor are not the same as the parameters which the Person class needs. However, you could do it if you passed 4 more parameters to the Student constructor as follows: public void student(int Student_Number, string Field, int Average,int Student_ID , string Name, string LastName, int Age ,int ID_Number) : base (Name, LastName, Age, ID_Number) { this.Student_Number = Student_Number; this.Field = Field; this.Average = Average; this.Student_ID = Student_ID; } If you do this, then you can dispense with a constructor which takes no parameters in the Person class.