基础

所述 base 关键字用于从基类访问成员。它通常用于调用虚方法的基本实现，或指定应调用哪个基本构造函数。

选择一个构造函数

public class Child : SomeBaseClass {
    public Child() : base("some string for the base class")
    {
    }
}

public class SomeBaseClass {
    public SomeBaseClass()
    {
        // new Child() will not call this constructor, as it does not have a parameter
    }
    public SomeBaseClass(string message)
    {
        // new Child() will use this base constructor because of the specified parameter in Child's constructor
        Console.WriteLine(message);
    }
}

调用虚方法的基本实现

public override void SomeVirtualMethod() {
    // Do something, then call base implementation
    base.SomeVirtualMethod();
}

可以使用 base 关键字从任何方法调用基本实现。这将方法调用直接绑定到基本实现，这意味着即使新的子类重写虚拟方法，仍将调用基本实现，因此需要谨慎使用。

public class Parent
{
    public virtual int VirtualMethod()
    {
        return 1;
    }
}

public class Child : Parent
{
    public override int VirtualMethod() {
        return 11;
    }

    public int NormalMethod()
    {
        return base.VirtualMethod();
    }

    public void CallMethods()
    {
        Assert.AreEqual(11, VirtualMethod());

        Assert.AreEqual(1, NormalMethod());
        Assert.AreEqual(1, base.VirtualMethod());
    }
}

public class GrandChild : Child
{
    public override int VirtualMethod()
    {
        return 21;
    }

    public void CallAgain()
    {
        Assert.AreEqual(21, VirtualMethod());
        Assert.AreEqual(11, base.VirtualMethod());

        // Notice that the call to NormalMethod below still returns the value
        // from the extreme base class even though the method has been overridden
        // in the child class.
        Assert.AreEqual(1, NormalMethod());
    }
}