拳击，非拳击和类型转换有什么区别 [英] what is the difference between Boxing,Un-Boxing and typecasting

问题描述

类型转换与装箱有什么主要区别，拆箱？

What are the main differences between typecasting and boxing ,unboxing??

推荐答案

类型转换是表达式到给定类型的转换，前提是类型是相互衍生，或存在合适的转换方法。例如，整数值可以转换为double，反之亦然：

Typecasting is a conversion of an expression to a given type, provided that the types are derived from each other, or a suitable conversion method exists. For example, an integer value can be cast to a double, and vice versa:

int i = 999;
double d = 123.456;
i = (int) d;
d = i; // Implicit cast

或

Or

private void myButton_Click(object sender, EventArgs e)
    {
    if (sender is Button)
        {
        Button b = (Button) sender;
        }
    }

或

Or

foreach (Control c in Controls)
    {
    if (c is TextBox)
        {
        TextBox tb = (TextBox) c;
        }
    }

您无法使用强制转换在没有定义转换或关系的类型之间进行更改。



装箱和拆箱是透明地在Reference类型中包含Value类型（例如整数或结构）的过程，以便它可以用作参考。这有点难以解释，所以看看这里：使用struct和class - 那是什么呢？ [ ^ ] - 有一个关于拳击的部分以及它是什么/为什么必要。

You cannot use casting to change between types where there is no defined conversion or relationship.

Boxing and unboxing are the process of "containing" a Value type (such as a integer, or struct) within a Reference type transparently so that it can be used as a reference. This is a bit complicated to explain, so have a look here: Using struct and class - what's that all about?[^] - there is a section on Boxing and what / why it is neccessary.

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