如何在 C# 中使用该类的单个实例在类中调用不同的构造函数？

Question

Code description

在这里，我创建了两个类 Program，其中 Main() 存在和 Customer Class，其中我有两个 Customer 类构造函数 1. 没有参数 2. 有参数。如何使用 Main 中创建的 Customer 类的单个实例 C1 调用两个构造函数？

Code

using System;
public class Program
{
    public static void Main()
    {

        Customer C1 = new Customer();
        C1.PrintFullName();
        C1 = new Customer();
        C1.PrintFullName();
    }
}

class Customer
{

    string _firstName;
    string _lastName;

    public Customer() : this("No firstname","No lastname")
    {
    }

    public Customer(string FirstName, string LastName)
    {
        this._firstName = FirstName;
        this._lastName = LastName;
    }

    public void PrintFullName()
    {
        Console.WriteLine("Full Name is {0}", this._firstName+" "+this._lastName);
    }
}

Answer 1

在创建一个新对象中固有地涉及一个类构造函数 - 所以没有针对现有实例运行构造函数的内置概念，除非你做了一些 非常 讨厌的事情你不应该做的事情。

如果您希望能够使用构造函数像那样设置所有属性，那么也许可以添加一个方法：

var obj = new SomeType();
obj.Init();
// ...
obj.Init("foo", "bar", 123);
// ...

或者：只需使用现有的构造函数并接受它将是具有不同引用的不同实例：

var obj = new SomeType();
// ...
obj = new SomeType("foo", "bar", 123);
// ...

Answer 2

您可以找到更多信息here：

using System;

public class Program
{
    public static void Main()
    {
        Customer C1 = new Customer("Bob", "Robert", "BobyBob 23, 41423");
        C1.PrintFullName();
        C1 = new Customer("Bob", "Robert");
        C1.PrintFullName();
    }
}

class Customer
{

    string _firstName;
    string _lastName;
    string _address;


    public Customer()
    {
        Console.WriteLine("I'm the last one :)");
        Console.WriteLine("Full Name is {0}", this._firstName+" "+this._lastName);
    }

    public Customer(string FirstName, string LastName) : this()
    {
        Console.WriteLine("I'm gonna call the constructor within the same class that has no parameters.");      
        _firstName = FirstName;
        _lastName = LastName;
    }

    public Customer(string FirstName, string LastName, string address) : this(FirstName, LastName)
    {
        Console.WriteLine("I'm gonna call the constructor within the same class that has 2 parameters that are of type string.");
        _address = _address;
    }

    public void PrintFullName()
    {
        Console.WriteLine("Full Name is {0}", this._firstName+" "+this._lastName);
    }
}