“进程由于 StackOverflowException 而终止”，其原因在以下代码中

Question

A class which in it of itself contains its own object instantiated,when creating an object of that class in main method in c#, it gives stackoverflowExeption. Why?? I want the reason for it, not the solution.Thanks

namespace project_1
{
class check
{
    check checkobject = new check();// Line-1

    /*I have not access Line-1 in main method.
     But due to Line-1 or Line-2, output says "Process is terminating due to StackOverflowException". Why??
     I do not need the solution, I want to know the reason for it.
     Removing " new check() " from Line-1, then it works fine.
     */
    public void Display() {
        Console.WriteLine("It worked");
    }
}
class DemoProgram
{
    static void Main(string[] args)
    {
        check ob1 = new check();// Line-2
        ob1.Display();
    }
}
}

Answer 1

This is because when you create a new check object from your main method, it triggers the initialization of the instance variable, checkobject , which again creates an object of class check. This is an infinite procedure, hence the memory alloted to your program is exhausted.

Answer 2

You call your class constructor every time the class is initialised. The line marked as line 1 is the one you shouldn't have. It means you call your constructor recursively.

Answer 3

If you try to debug your program, you see the similar output to the following. If you know almost nothing why it happens, at least you can guess something is wrong subject to the constructor.

Compilation succeeded - 1 warning(s)

jdoodle.cs(5,11): warning CS0414: The private field `check.checkobject' is assigned 
                  but its value is never used


Stack overflow: IP: 0x5647646e1705, fault addr: 0x7fffc422eff8
Stacktrace:
  at <unknown> <0xffffffff>
  at (wrapper alloc) object.AllocSmall (intptr,intptr) <0x00103>
  <...>
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0
  ........
  ........
  ........
  ........
  ........
  at check..ctor () [0x00000] in <db1fd2bd96e041fab014c4ec28898e03>:0

  output Limit reached.

Answer 4

Your problem is an endless recursion caused by a field initializer .

Example

public class Test
{
   Type FieldName = SomeValue;

A field initializer is executed before constructor bodies. The important take-home point here is, they are always executed.

Which means you can't do this, it runs when the class initialises.

check checkobject = new check();

Every time you new up (initialise) this class , it's going to run the above code, which by its very nature new's up another instances of itself due to the *field initializers, which in-turns runs the above again so-on-and-so-forth until you run out of stack .

If you really want a self-referencing property like this, and you want it initialised (in an automatic sense), use a lazy loading technique, eg.

private Check _checkObject;

public Check CheckObject => _checkObject?? (_checkObject = new Check());