As for the local variable passing in the stream

Question

I find it difficult to understand the unexpected output for the following program:

class ThreadTest
{
     static void Main()
     {
          for(int i = 0; i < 10; i++)
               new Thread(() => Console.Write(i)).Start();
     }

}

Requests: Do different codes running on different threads have separate stacks? If so, should the variables retain their values, since int is a value type?

Answer 1

Each thread gets its own stack. The problem you are facing has nothing to do with the stack. The problem is how it generates code for an anonymous delegate. Use a tool, such as a reflector, to understand the code that it generates. The following issues will be fixed:

static void Main() 
        {
            for (int i = 0; i < 10; i++)
            {
                int capture = i;
                new Thread(() => Console.Write(capture)).Start();
            }
        } 

Under the hood

, ( case i) , , , . , - i. :

class SomeClass
{
    public int i { get; set; }

    public void Write()
    {
        Console.WriteLine(i);
    }
}

:

SomeClass someObj = new SomeClass();
for (int i = 0; i < 10; i++)
{
    someObj.i = i;
    new Thread(someObj.Write).Start();
}

, , , . , :

for (int i = 0; i < 10; i++)
{
    SomeClass someObj = new SomeClass();
    someObj.i = i;
    new Thread(someObj.Write).Start();
}

SomeClass. , , . , .

, .

Answer 2

, . . :

class ThreadTest
{
    static void Main()
    {
         for(int i = 0; i < 10; i++)
         {
              int j = i;
              new Thread(() => Console.Write(j)).Start();
         }
    }
} 

? , . int j = i;, . , .