在C＃愚蠢的继承问题 [英] Stupid inheritance question in C#

问题描述

我敢肯定，这是不可能的，但在这里不用..

I'm pretty sure this is impossible, but here goes..

我在C＃中的自定义类叫做Person其中有一些属性如年龄，身高等。

I have a custom class in C# called Person which has a few properties such as Age, Height etc.

然后我做了一个名为雇员的新类，它继承Person，但我还没有添加任何其他属性员工。因此，它基本上只是一个人还在，但其所谓的员工。

I then make a new class called Employee which inherits from Person but I don't yet add any other properties to Employee. So its basically just a Person still, except its called an Employee.

现在说我有一个名为SomePerson人的一个实例。如何创建具有所有从它继承了人的价值观的新Employee实例，设置里面的人SomePerson。就像从个人浇铸成一个雇员。但是没有我不必手动指定需要设置..

Now say I have an instance of Person called SomePerson. How can I create a new Employee instance that has all of the values it inherited from Person, set to those inside SomePerson. Like casting from a Person into an Employee.. But without me having to manually specify each and every property that needs to be set..

喜欢的东西每一个属性。

Something like..

Employee NewEmployee = (Employee)SomePerson;

不过，当然，你得到错误说无法一个人转换成员工等。

But of course you get the error saying "Can't convert a Person into an Employee" etc.

时AutoMapper唯一可行的解​​决方案，做这样的事情，如果你说有在所涉及的对象??

Is AutoMapper the only practical solution to do things like this if you say had 300 properties in the involved objects??

更新：

自动映射似乎不处理我的对象。

Auto-Mapper doesn't seem to handle my objects..

Employee SomeEmployee = EmployeeRepository.GetEmployee(SomeEmployeeID);

// Populate the ViewModel with the Person fetched from the db, ready for editing..
VMEmployee EmployeeToEdit = Mapper.Map<Employee, VMEmployee>(SomeEmployee);


// ViewModel based on Employee with Validation applied..
[MetadataType(typeof(Employee_Validation))]
public class VMEmployee : Employee
{
    // Absolutely nothing here
}

，其中员工，是自动通过LINQ生成到SQL ..

where "Employee" is auto-generated by LINQ to SQL..

推荐答案

AutoMapper是在这种情况下，一个很好的解决方案。如果你不打算使用属性映射框架，你不想创建一个拷贝构造函数公职人员（人人），或隐式/显式转换，怎么回事你期望在整个复制的属性。现实你可以

AutoMapper is a good solution in this case. If you're not going to use a property mapping framework, and you're not willing to create a copy constructor public Employee(Person person), or an implicit/explicit conversion, how else do you expect to copy the properties across. Realistically you could

1.Reflection

1.Reflection

public void Map<TSource, TDestination>(TSource source, TDestination destination)
{
  var props = typeof(TSource).GetProperties(BindingFlags.Public | BindingFlags.Instance);
  var type = typeof(TDestination);

  foreach (var prop in props)
  {
    object value = prop.GetValue(source, null);

    var prop2 = type.GetProperty(prop.Name);
    if (prop2 == null)
      continue;

    if (prop.PropertyType != prop2.PropertyType)
      continue;

    prop2.SetValue(destination, value, null);
  }
}

2.复印构造

2.Copy Constructor

public Employee(Person person)
{
  // Copy properties
}

3.Implicit /显式转换

3.Implicit/Explicit Conversion

public static implicit operator Employee(Person person)
{
  // Build instance and return
}

4.AutoMapper

4.AutoMapper

Mapper.Map<Person, Employee>(person);

3/4 5.Combination：

5.Combination of 3/4:

public static implicit operator Employee(Person person)
{
  return Mapper.Map<Person, Employee>(person);
}

隐式/显式转换操作符的说明：我相信在使用这些你赢了'T被生成符合CLS的代码。

A note on implicit/explicit conversion operators: I believe in using these you won't be generating CLS-compliant code.

作为@米奇小麦已经表示，如果你有超过300个属性的对象，我会重新考虑是什么对象实际上代表。重构重构重构。

As @Mitch Wheat has already said, if you have an object with over 300 properties, I would reconsider what that object actually represents. Refactor refactor refactor.

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