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Accepted
dgzargo
Asked:2020-02-05 03:08:55 +0000 UTC2020-02-05 03:08:55 +0000 UTC

带有可选参数的 C# 构造函数继承

  • 772
abstract class MyClass
{
  int Param1 {get; set;} 
  int Param2 {get; set;} 
  MyClass(int param1 = 4, int param2 = 10)
  {
  this.Param1 = param1;
  this.Param2 = param2;
  }
}

class Class1 : MyClass //переопределяю значения по-умолчанию
{
  int Param3 {get; set;} 
  Class1(int param1 = 4, int param2 = 10, int param3 = 2):base(param1, param2)
  {
  this.Param3 = param3;
  }
}

需要在子类中做可选参数，不重复参数中常量的设置
；如果调用时不指定参数，则取自父构造函数

通过制作可选参数可以手动实现类似的行为： 

public Class1(int param1, int param2, int param3 = 2):base(param1, param2)
{
  this.Param3 = param3;
}
public Class1(int param1, int param3 = 2):base(param1: param1)
{
  this.Param3 = param3;
}
public Class1(int param3 = 2):base()
{
  this.Param3 = param3;
}
c#

2 个回答

  1. 我认为没有比这更好的方法了：https ://ideone.com/R4imt8

    abstract class MyClass
{
  public const int Param1Default = 4;
  public const int Param2Default = 10;

  int Param1 { get; set; }
  int Param2 { get; set; }

  public MyClass(int param1 = Param1Default, int param2 = Param2Default)
  {
    this.Param1 = param1;
    this.Param2 = param2;
  }
}

class Class1 : MyClass
{
  int Param3 { get; set; }

  public Class1
  (
    int param1 = MyClass.Param1Default,
    int param2 = MyClass.Param1Default,
    int param3 = 2
  )
  : base(param1, param2)
  {
    this.Param3 = param3;
  }
}
    • 4
  2. Best Answer

    您可以将参数设为可为空的类型：

    abstract class MyClass
{
  public const int Param1Default = 4;
  public const int Param2Default = 10;

  int Param1 { get; set; }
  int Param2 { get; set; }

  protected MyClass(int? param1 = null, int? param2 = null)   
  {
    Param1 = param1 ?? Param1Default;
    Param2 = param2 ?? Param2Default;
  }
}

class Class1 : MyClass
{
  public const int Param3Default = 2;

  int Param3 { get; set; }

  public Class1(int? param1 = null, int? param2 = null, int? param3 = null)
  : base(param1, param2)
  {
     Param3 = param3 ?? Param3Default;
  }
}
    • 1

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