装箱和拆箱会在阵列中发生吗?

问题描述

我是编程新手，

按照 MSDN ，

我知道我们可以将任何对象存储在arraylist中，因为system.object是所有所有类型的基础.装箱和拆箱发生在阵列列表中.我同意这一点.

I knew We can store any objects in an arraylist, because system.object is a base for all all types. Boxing and unboxing happens in array list. I agree with that.

装箱和拆箱会在阵列中发生吗?因为我们可以像下面那样创建对象数组

Will boxing and unboxing happens in an array? Because We can create object array like below

object[] arr = new object[4] { 1, "abc", 'c', 12.25 };

我是否了解装箱和拆箱是在这种阵列中进行的?

Is my understanding that boxing and unboxing happens in such array correct?

推荐答案

数组本身已经是引用类型，数组本身没有装箱.但是，由于您的某些元素是值类型(int，double和char)，而您的数组类型是object，因此将对所述元素进行装箱.当您要提取它时，需要将其拆箱:

The Array itself is already a reference type, there is no boxing on the array itself. But, as some of your elements are value types (int, double and char), and your array type is object, a boxing will occur for the said element. When you'll want to extract it, you'll need to unbox it:

var num = (int)arr[0];

您可以在生成的IL中看到它:

You can see it in the generated IL:

IL_0000: ldarg.0
IL_0001: ldc.i4.4
IL_0002: newarr [mscorlib]System.Object
IL_0007: dup
IL_0008: ldc.i4.0
IL_0009: ldc.i4.1
IL_000a: box [mscorlib]System.Int32 // Boxing of int
IL_000f: stelem.ref
IL_0010: dup
IL_0011: ldc.i4.1
IL_0012: ldstr "abc"
IL_0017: stelem.ref
IL_0018: dup
IL_0019: ldc.i4.2
IL_001a: ldc.i4.s 99
IL_001c: box [mscorlib]System.Char
IL_0021: stelem.ref
IL_0022: dup
IL_0023: ldc.i4.3
IL_0024: ldc.r8 12.25
IL_002d: box [mscorlib]System.Double
IL_0032: stelem.ref
IL_0033: stfld object[] C::arr
IL_0038: ldarg.0
IL_0039: call instance void [mscorlib]System.Object::.ctor()
IL_003e: nop
IL_003f: ret

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