为什么在将C＃代码编译为IL时创建.ctor（）？ [英] Why is the .ctor() created when I compile C# code into IL?

问题描述

使用这个简单的C＃代码，我运行 csc hello.cs;。 ildasm /out=hello.txt hello.exe 。

With this simple C# code, I run csc hello.cs; ildasm /out=hello.txt hello.exe.

class Hello
{
    public static void Main()
    {
        System.Console.WriteLine("hi");
    }
}

这是ildasm的IL代码。

This is the IL code from ildasm.

.class private auto ansi beforefieldinit Hello
       extends [mscorlib]System.Object
{
  .method public hidebysig static void  Main() cil managed
  {
    .entrypoint
    // Code size       13 (0xd)
    .maxstack  8
    IL_0000:  nop
    IL_0001:  ldstr      "hi"
    IL_0006:  call       void [mscorlib]System.Console::WriteLine(string)
    IL_000b:  nop
    IL_000c:  ret
  } // end of method Hello::Main

  .method public hidebysig specialname rtspecialname 
          instance void  .ctor() cil managed
  {
    // Code size       7 (0x7)
    .maxstack  8
    IL_0000:  ldarg.0
    IL_0001:  call       instance void [mscorlib]System.Object::.ctor()
    IL_0006:  ret
  } // end of method Hello::.ctor

} // end of class Hello

.method公共实例void .ctor（）代码的用途是什么？

What's the use of .method public instance void .ctor() code? It doesn't seem to do anything.

推荐答案

它是默认的无参数构造函数。你是对的；它什么也没做（除了传递给基本的 Object（）构造函数之外，它本身也没有任何特殊作用）。

It's the default parameterless constructor. You're correct; it doesn't do anything (besides passing on to the base Object() constructor, which itself doesn't do anything special either anyway).

如果未定义任何其他构造函数，则编译器始终为非静态类创建默认构造函数。然后，将任何成员变量初始化为默认值。这样就可以做到

The compiler always creates a default constructor for a non-static class if there isn't any other constructor defined. Any member variables are then initialized to defaults. This is so you can do

new Hello();

而不会出错。

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