没有在C＃中接受0参数的构造方法

Question

I've got this error while I program in C#: 'BankSystem.Account' does not contain a constructor that takes 0 arguments

My classes are:

Firstly, the Account class:

 public abstract class Account : IAccount
{

    private static decimal minIncome = 0;
    private static int minAge = 18;

    private string name;
    private string address;
    private decimal age;
    private decimal balance;

    public Account(string inName, decimal inAge, decimal inBalance, string inAddress)
    {
        if (AccountAllowed(inBalance, inAge))
        {
            name = inName;
            address = inAddress;
            balance = inBalance;
            age = inAge;

            Console.WriteLine("We created the account. \nName is " + name + " \nThe address is: "
            + address + "\nThe balance is " + balance);

        }
        else
        {
            Console.WriteLine("We cann't create the account. Please check the balance and age!");
        }
    }

    //public CustomerAccount(string newName, decimal initialBalance)

    public Account(string inName, decimal initialBalance)
    {
    }

Secondly, The CustomerAccount class:

 public class CustomerAccount : Account
{
    private decimal balance = 0;
    private string name;

    public CustomerAccount(string newName, decimal initialBalance)
    {
        name = newName;
        balance = initialBalance;
    }

    public CustomerAccount(string inName, decimal inAge, decimal inBalance, string inAddress)
        : base(inName, inAge)
    {

        // name = inName;
        //age = inAge;
    }

    public CustomerAccount(string inName, decimal inAge)
        : base(inName, inAge)
    {

        // name = inName;
        //age = inAge;
    } ......

Answer 1

Because you have defined constructors with parameters in your class, you will not get the default constructor by default.

Your account class has defined constructors:

public Account(string inName, decimal inAge, decimal inBalance, string inAddress)
public Account(string inName, decimal initialBalance)

you may define a default constructor like.

public Account() 
{
}

The error you are getting is because, your below constructor for CustomerAccount is implicitly calling a default constructor for the Account base class, as you have not specified any other base constructor eg :base(arg1,arg2);

 public CustomerAccount(string newName, decimal initialBalance)
    {
        name = newName;
        balance = initialBalance;
    }

The above is same as:

 public CustomerAccount(string newName, decimal initialBalance) : base()

Answer 2

You need to 'chain' to the base constructor here too:

public CustomerAccount(string newName, decimal initialBalance)
    : base(newName, 0)    // something like this
{
    name = newName;
    balance = initialBalance;
}

Answer 3

Simple. Your Account class doesn't contain a contructor with Zero arguments eg

public Account()
{

}

The answer is in the error message.

When you create a new instance of the Account class pass in the correct parameters eg

Account account = new Account("John Smith", 20.00);

Or create a constructor that takes zero arguments.

Answer 4

You are initializing your Account class like this

new Account();

but should do

new Account("name", ...);

according to your constructor definition.