string, value type reference type problem

duck042432

Look at this question
using System;
class Class1 {

 static void StringConvert (string str)
{
           str = "string being converted.";
      }
 static void Main ()
{
 string str1 = "str";

 StringConvert (str1);
  Console.WriteLine (str1);
}
}

  The result output is: str

  Still about value types and reference types
    Everyone knows that string is a reference type. I can't figure this out.
my thoughts :

 1, str1 points to the string value in the managed heap as str;
2, the static method StringConvert in memory calls str1 (because it is a reference, it must be of type string)
3. Because str1 is modified in the method, a string type space is re-allocated in the managed heap, str1 points to the modified memory, that is, "string being converted."
4, the Console.WriteLine method calls the memory pointed to by str1, which outputs "string being converted.";




Doubt:
After str1 is modified, it still points to "str", then the modified "string being converted."; who pointed to this memory, seems to disappear, how to output

yujunziling

C # 's string is a bit special.It is actually a value type, but has the characteristics of some reference types, that is, it is wrapped with a layer of object characteristics outside of its essence.

sumu007

string is a special reference type,
string str1 = "str";
static void StringConvert (string str)
{
str = "string being converted.";
}
In StringConvert function str = "string being converted."; Is another string,
When the StringConvert function is called, str passes parameters, not a reference, but another copy of a string.
The original string has not changed

duck042432

Kind of understand
 And static void StringConvert (int i)
{

}
Is a reason

sumu007

Basically right

vampire_66

Use ref

vampire_66

using System;
class Class1 {

 static void StringConvert (ref string str)
{
           str = "string being converted.";
      }
 static void Main ()
{
 string str1 = "str";

 StringConvert (ref str1);
  Console.WriteLine (str1);
}
}

wenmy715

The reference type is a handle / object pair, handle is equivalent to a pointer, and object is a piece of memory space on the managed heap.
static void StringConvert (string str) The parameter passed is a handle,
The str in the function body is actually just a copy of the handle of the external strl reference type. Changing the content pointed to by str does not affect the pointing of str1.

芬恩克莱尔

str and str1 point to the same thing and are references to the same thing, but they are not the same thing.

And after:
str = "string being converted.";

Point str to something else, while str1 still points to "str".

The special feature of string is that its object cannot be modified, and it is indeed a reference type.

As in the same, you can't see that the array is a reference type in this experiment:

int [] arr = new int [] {0,1};

int [] arr1 = arr;
arr1 = new int [0];

Does the assignment of arr1 affect arr?

However, this way we can see that the array is a reference type:

int [] arr = new int [] {0,1};

int [] arr1 = arr;
arr [0] = 5;

However, for string types, there is no such method at all. So I can't see it.


As for the nonsense guy on the first floor, you can just ignore it ...

kalian2000

String is a reference type. This is not a doubt, but it has some special characteristics with other reference types.

As for the reason, the芬恩克莱尔brother upstairs has made it very clear ...