用is和as进行C#强制转换 [英] c# casting with is and as

问题描述

我需要一些帮助.这很容易.我有这段代码，我想讨论一下它是否正确，或者您是否建议一种更好的方法.我对答案有一个主意，但我希望看到您的答案.在这里

I need some help. It is pretty easy. I have this piece of code, and I would like to discuss if it is correct, or if you suggest a better way to do it. I have an idea about the answer but I would like to see your answers. here it goes

if (myObject is ClassA)
{
    var myObjectA = myObject as ClassA;
    myObjectA?.MethodJustInA();
}
else if (myObject is ClassB)
{
    var myObjectB = myObject as ClassB;
    myObjectB?.MethodJustInB();
    myObjectB?.OtherMethodJustInB();
}

我认为没有必要在每次之后都创建一个新对象，只需这样做:

I think there is no need to create a new object after every if, just doing:

(ClassB)myObjectB.MethodJustInB();

并且不需要检查它是否为null，因为它是否在if is内，因为它不为空

And there is no need to check it is null since if it is within the if is because is not null

谢谢

推荐答案

可能有一些优化.

• 如果 myObject是ClassA ，则不需要进行强制转换.相反，您可以直接进行强制转换: var myObjectA =(ClassA)myObject; .
• 既然是这种情况，您只需调用一个方法，就无需分配新变量:((ClassA)myObject)?. MethodJustInA(); .li>
• 并且由于如果 myObject 为null，则 myObject是ClassA 的计算结果为false，因此您无需再次进行检查:((ClassA)myObject).MethodJustInA(); .

• If myObject is ClassA, you don't need the soft cast. Instead you can do the cast directly: var myObjectA = (ClassA)myObject;.
• Since that is the case, and you just call a single method, you don't need to assign a new variable: ((ClassA)myObject)?.MethodJustInA();.
• And because myObject is ClassA evaluates to false if myObject is null, you don't need to do the check again: ((ClassA)myObject).MethodJustInA();.

所以:

if (myObject is ClassA)
{
    ((ClassA)myObject).MethodJustInA();
}
else if (myObject is ClassB)
{
    var myObjectB = (ClassB)myObject;
    myObjectB.MethodJustInB();
    myObjectB.OtherMethodJustInB();
}

这篇关于用is和as进行C#强制转换的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！