C#中struct与class
请问结构类型new 与不new 在内存中有什么区别吗?值类型是在栈里面分配空间,结构是值类型如果new了后还是在栈里面分配空间吗?
下面是两份代码,第一份结构类型没有new直接给它里面的引用类型传引用。第二份是结构类型new了后在给它里面的引用类型传引用。从IL代码中我们可以看到是有区别的,因为对IL还不太熟悉,不知道它们内存怎么分配的,而且也不知道是在什么时候分配的,所以望高人指点。
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
namespace StructAndClass
{
class Program
{
static void Main(string[] args)
{
ClassText classText;
classText = new ClassText();
classText.num = 5;
classText.name = "Hello";
StructText structText;
structText.classText = classText;
}
}
public class ClassText
{
public int num;
public string name;
}
public struct StructText
{
public ClassText classText;
public int n;
}
}
Main函数的IL代码
.method private hidebysig static void Main(string[] args) cil managed
{
.entrypoint
// 代码大小 34 (0x22)
.maxstack 2
.locals init (class StructAndClass.ClassText V_0,
valuetype StructAndClass.StructText V_1)
IL_0000: nop
IL_0001: newobj instance void StructAndClass.ClassText::.ctor()
IL_0006: stloc.0
IL_0007: ldloc.0
IL_0008: ldc.i4.5
IL_0009: stfld int32 StructAndClass.ClassText::num
IL_000e: ldloc.0
IL_000f: ldstr "Hello"
IL_0014: stfld string StructAndClass.ClassText::name
IL_0019: ldloca.s V_1
IL_001b: ldloc.0
IL_001c: stfld class StructAndClass.ClassText StructAndClass.StructText::classText
IL_0021: ret
} // end of method Program::Main
第二份代码
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
namespace StructAndClass
{
class Program
{
static void Main(string[] args)
{
ClassText classText;
classText = new ClassText();
classText.num = 5;
classText.name = "Hello";
StructText structText = new StructText();
structText.classText = classText;
int x = structText.n;
}
}
public class ClassText
{
public int num;
public string name;
}
public struct StructText
{
public ClassText classText;
public int n;
}
}
Main函数的IL代码
.method private hidebysig static void Main(string[] args) cil managed
{
.entrypoint
// 代码大小 42 (0x2a)
.maxstack 2
.locals init (class StructAndClass.ClassText V_0,
valuetype StructAndClass.StructText V_1)
IL_0000: nop
IL_0001: newobj instance void StructAndClass.ClassText::.ctor()
IL_0006: stloc.0
IL_0007: ldloc.0
IL_0008: ldc.i4.5
IL_0009: stfld int32 StructAndClass.ClassText::num
IL_000e: ldloc.0
IL_000f: ldstr "Hello"
IL_0014: stfld