C# 是否可以从指向子类对象的父类类型引用变量访问不在父类中的子类成员？
根据我的理解，如果我有一个指向子类对象的父类类型引用变量：C# 是否可以从指向子类对象的父类类型引用变量访问不在父类中的子类成员？,c#,asp.net,.net,oop,inheritance,C#,Asp.net,.net,Oop,Inheritance,根据我的理解，如果我有一个指向子类对象的父类类型引用变量： ParentClass obj= new ChildClass(); obj.OnlyMembersThatHavebeenDerivedFromParentAreAvailable// am i wrong? 在下面的示例中，我从 我应该无法访问年度日历 派生类： public class FullTimeEmployee : Employee { public int AnnualSalary { g
ParentClass obj= new ChildClass();
obj.OnlyMembersThatHavebeenDerivedFromParentAreAvailable// am i wrong?
public class FullTimeEmployee : Employee
{
public int AnnualSalary { get; set; }
}
public class PartTimeEmployee : Employee
{
public int HourlyPay { get; set; }
public int HoursWorked { get; set; }
}
Employee employee = null;
employee = new FullTimeEmployee
{
Id = Convert.ToInt32(reader["Id"]),
Name = reader["Name"].ToString(),
Gender = reader["Gender"].ToString(),
DateOfBirth = Convert.ToDateTime(reader["DateOfBirth"]),
Type = EmployeeType.FullTimeEmployee,
AnnualSalary = Convert.ToInt32(reader["AnnualSalary"]) // how is AnnualSalary available here?
};
public class FullTimeEmployee : Employee
{
public int AnnualSalary { get; set; }
}
public class PartTimeEmployee : Employee
{
public int HourlyPay { get; set; }
public int HoursWorked { get; set; }
}
Employee employee = null;
employee = new FullTimeEmployee
{
Id = Convert.ToInt32(reader["Id"]),
Name = reader["Name"].ToString(),
Gender = reader["Gender"].ToString(),
DateOfBirth = Convert.ToDateTime(reader["DateOfBirth"]),
Type = EmployeeType.FullTimeEmployee,
AnnualSalary = Convert.ToInt32(reader["AnnualSalary"]) // how is AnnualSalary available here?
};
public class Employee
{
private int _id;
private string _name;
private string _gender;
private DateTime _dateOfBirth;
[DataMember(Order = 1)]
public int Id
{
get { return _id; }
set { _id = value; }
}
[DataMember(Order = 2)]
public string Name
{
get { return _name; }
set { _name = value; }
}
[DataMember(Order = 3)]
public string Gender
{
get { return _gender; }
set { _gender = value; }
}
[DataMember(Order = 4)]
public DateTime DateOfBirth
{
get { return _dateOfBirth; }
set { _dateOfBirth = value; }
}
[DataMember(Order = 5)]
public EmployeeType Type { get; set; }
}
public class FullTimeEmployee : Employee
{
public int AnnualSalary { get; set; }
}
public class PartTimeEmployee : Employee
{
public int HourlyPay { get; set; }
public int HoursWorked { get; set; }
}
Employee employee = null;
employee = new FullTimeEmployee
{
Id = Convert.ToInt32(reader["Id"]),
Name = reader["Name"].ToString(),
Gender = reader["Gender"].ToString(),
DateOfBirth = Convert.ToDateTime(reader["DateOfBirth"]),
Type = EmployeeType.FullTimeEmployee,
AnnualSalary = Convert.ToInt32(reader["AnnualSalary"]) // how is AnnualSalary available here?
};
你是对的，你不能写：
employee.AnnualSalary = 1234;
您只是使用对象初始值设定项来初始化
FullTimeEmployee基本上，您正在执行以下操作：
FullTimeEmployee employeeTemp = new FullTimeEmployee();
employeeTemp .AnnualSalary =2000;
Employee employee =employeeTemp;
再一次，这不是你的情况…
方法的返回类型可能是Employee，但实际返回的对象可能是其他对象（派生类）。
在这种情况下，您可以安全地将对象强制转换为派生类型。
检查以下示例
namespace CastExample
{
class Program
{
static void Main(string[] args)
{
Employee emp = GetEmployee();
FullTimeEmployee full = (FullTimeEmployee)emp;
System.Console.WriteLine(full.AnnualSalary);
PartTimeEmployee part = (PartTimeEmployee)emp;//InvalidCastException
System.Console.ReadLine();
}
static Employee GetEmployee()
{
return new FullTimeEmployee() { Name = "George", AnnualSalary = 1234 };
}
}
public class Employee
{
public string Name;
}
public class FullTimeEmployee : Employee
{
public int AnnualSalary { get; set; }
}
public class PartTimeEmployee : Employee
{
public int HourlyPay { get; set; }
public int HoursWorked { get; set; }
}
}
选中此项：
@Marc Gravell的回答解释了为什么你可以这样做，但要特别注意@Tamas Czinege的回答（我在这里再次引用） 成员可访问性不是安全功能。它是用来保护的 程序员反对他自己。它有助于实施 封装，但它决不是一个安全特性
你有什么问题吗？它编译吗？我没有在visual studio中重新创建它。我看了同一个博客的视频教程（使用了和那个博客上完全相同的代码），他成功地编译并运行了它。所以，是的，它确实可以编译。但是为什么呢？哦！我现在明白了。该死的初始化语法！顺便说一句，以确保我的方法是否返回此
employee