C# 数组索引器

Question

我想知道：C#数组索引器是如何实现的？您可以使用从 ulong 到 sbyte 的基本上每个整数值对 C# 数组进行索引，内部实现是否每次都简单地转换为通用类型？

要明确这一点：

ulong i = 10;
var o = myArray[i];

被翻译成类似的东西：

ulong i =10;
var o = myArray[(int /*or whatver is the default type used*/)i];

?

Answer 1

数组索引器的类型是整数，所以是的，该值将被转换为整数。您可以通过检查 IL 代码来验证这一点。给出这个例子：

var myArray = new[]{ 1,2,3 };
ulong i = 10;
var o = myArray[i];

这将编译成：

.method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       29 (0x1d)
  .maxstack  3
  .locals init ([0] int32[] myArray,
           [1] uint64 i,
           [2] int32 o)
  IL_0000:  nop
  IL_0001:  ldc.i4.3
  IL_0002:  newarr     [mscorlib]System.Int32
  IL_0007:  dup
  IL_0008:  ldtoken    field valuetype '<PrivateImplementationDetails>'/'__StaticArrayInitTypeSize=12' '<PrivateImplementationDetails>'::E429CCA3F703A39CC5954A6572FEC9086135B34E
  IL_000d:  call       void [mscorlib]System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(class [mscorlib]System.Array,
                                                                                                      valuetype [mscorlib]System.RuntimeFieldHandle)
  IL_0012:  stloc.0
  IL_0013:  ldc.i4.s   10
  IL_0015:  conv.i8
  IL_0016:  stloc.1
  IL_0017:  ldloc.0
  IL_0018:  ldloc.1
  IL_0019:  conv.ovf.i.un
  IL_001a:  ldelem.i4
  IL_001b:  stloc.2
  IL_001c:  ret
} // end of method Program::Main

转换发生在 IL_0019，使用 conv.ovf.i.un 指令。

Converts the unsigned value on top of the evaluation stack to signed native int, throwing OverflowException on overflow.

C# 数组索引器

C# Array Indexer

c#

arrays

casting

indexer