C＃immutable int [英] C# immutable int

问题描述

在Java中，字符串是不可变的。如果我们有一个字符串并对其进行更改，我们将获得由同一个变量引用的新字符串：

  String str =abc ; 
 str + =def; // now str指的是堆中包含abcdef的另一块
 //而abc仍然在堆中的某个地方，直到GC 
   
 
 
 据说 int和double在C＃中是不可变的。这是否意味着当我们有int并且稍后更改它时，我们会得到同一个变量指向的新int？同样的事情，但有堆栈。
  int i = 1; 
 i + = 1; //同样的事情：在堆栈中有值2连接变量
 // i，堆栈中某处有值1 
  
这是正确的吗？如果没有，以什么方式是int immutable？
解决方案
你没有改变（并且不能关于int的一些事情;您已分配新 int值（并丢弃旧值）。因此它是不可变的。
 
 
 
考虑一个更复杂的结构：
  var x = new FooStruct（123）; 
 x.Value = 456; // mutate 
 x.SomeMethodThatChangedInternalState（）; // mutate 
 
 x = new FooStruct（456）; // **不**变异;这是*重新分配* 
  
但是，这里没有指向。结构直接在堆栈上（在本例中）：不涉及引用。
 
In Java strings are immutable. If we have a string and make changes to it, we get new string referenced by the same variable:
String str = "abc";
str += "def"; // now str refers to another piece in the heap containing "abcdef"
              // while "abc" is still somewhere in the heap until taken by GC
It's been said that int and double are immutable in C#. Does it mean that when we have int and later change it, we would get new int "pointed" by the same variable? Same thing but with stack.
int i = 1;
i += 1; // same thing: in the stack there is value 2 to which variable
        // i is attached, and somewhere in the stack there is value 1
Is that correct? If not, in what way is int immutable?
解决方案
You haven't changed (and cannot change) something about the int; you have assigned a new int value (and discarded the old value). Thus it is immutable.

Consider a more complex struct:
var x = new FooStruct(123);
x.Value = 456; // mutate
x.SomeMethodThatChangedInternalState(); // mutate

x = new FooStruct(456); // **not** a mutate; this is a *reassignment*
However, there is no "pointing" here. The struct is directly on the stack (in this case): no references involved.

                        
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