How can I persist data between 2 appliaiton

Question

Hi,

I have 3 application

1- C# window application1
2- C# window application2
3- Class library
I am Passing data from application 1 to class library and I want this data from application 2. But I am not getting

For ex My class library have one class 

public class1
{
  public bool Flag = false;
  public void hello(bool f)
  {
   
    Flag = f;
  } 
}

application 1

class1 cs = new class1();
cs.hello(true);

but from application 2 I am always getting Flag value false event I passed true
Please suggest how can i persist value of flag.

Thanks