Should the base Keyword be used?

When calling methods on a base class from a derived class, should the 'base' keyword be used? It seems using the base keyword would increase code readability but for me 开发者_Go百科so far, when I exclude it, there is no affect on code compilation and execution.

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The base keyword is important when overriding methods:

override void Foo()
{
  base.Foo();
  // other stuff
}

I never use it for anything else.

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You should not use base unless you specifically mean "Even if there is a method in this class that overrides the base implementation, I want to call the base implementation and ignore the one on this class".

Using base bypasses the virtual dispatch mechanism that is so important in polymorphism by causing a call instruction to be emitted rather than callvirt.

So saying base.Foo() is very, very different in semantics to saying this.Foo(). And you almost always want the latter.

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It does matter if you have overridden a method:

class Test { 
   public override string ToString() { return "Hello World"; }
   public string M1() { return ToString(); } // Test.ToString
   public string M2() { return base.ToString(); } // System.Object.ToString
   static void Main() { 
       var t = new Test();
       Console.WriteLine("M1: {0}", M1()); // Hello World
       Console.WriteLine("M2: {0}", M2()); // Test
   }
}

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Sometimes, you can't avoid it. If your class overrides an implementation of a function from the base class, then without the base keyword, calls could be dispatched to the implementation in your class.

In all other situations, it's a matter of style (much like "Should I prefix all calls/field accesses with this). I say "No" as it tends to increase code clutter without significantly helping readability, but "Yes" is just as valid an answer - especially if you have a class with many overridden methods, but will be including many calls upwards in the hierarchy.

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I'd say no. The main purpose of base is to allow you to call base class versions of virtual methods without virtual dispatch taking place. Personally, I consider any other use of base to be an abuse - it doesn't really buy you anything over just calling a method as usual (or using this), and it will break if you later override the called method in your class.

Also, there is a very real difference if the method is virtual, and someone down the line overrides it. To give an example, say you write this (in a reusable class):

class Base {
   public virtual void Foo() {}
}

class Derived : Base {
   void Bar() { base.Foo(); }
}

And later on someone else who uses your class writes:

class MoreDerived : Derived {
   public override void Foo() {}
}

Now your base.Foo() will not do dynamic dispatch, and therefore will not call the overridden Foo() in MoreDerived. It may be what you actually want, but I'd find such a code very suspect if that was the intent.

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There are times when the base keyword has to be used such when you want to call a method in the base class that's been overidden in the derived class.

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Look to this example:

    class ParentClass {
        public virtual void A() {
            // Some operations
        }
    }

    class ChildClass : ParentClass {
        public override void A()
        {
            base.A();
        }
    }

If we execute ChildClass.A() then we have some operations, but in this case:

    class ParentClass {
        public virtual void A() {
            Console.WriteLine("ParentClass.A");
        }
    }

    class ChildClass : ParentClass {
        public override void A()
        {
            A();
        }
    }

we have StackOverflowException, because ChildClass.A() execute ChildClass.A()

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There will be no difference in the generated IL in most cases.

However, if you are overriding a virtual method in the base class, or hiding a method in the base class using the "new" keyword, then this is required, and will change the meaning, since it explicitly calls the base class method.

However, it is often a good idea, since it improves readability, and hence maintainability. If you are explicitly wanting to call a method in the base class, then I feel that it's a good idea, even when not technically required.