Are you familiar with [ThreadStatic]?

ThreadStatic is a super-cool concept if you have a static variable. you can make it static "per-thread" by placing the attribute on top.  This is one easy way to get around the thread-safety issues of working with statics - as they are per-thread, you do not have to take a lock when updating them.

[ThreadStatic]

private static string Foo;

Here each thread accessing this field will have its own copy and is not visible to other threads. 

Initialization =>  The initial value of thread static field is only applicable to the first accessing thread. And for all the subsequent threads it will be initialized to null. 

    class Program
    {
        static void Main(string[] args)
        {            
            Thread th = new Thread(new ThreadStart( ThreadFun ));
            Console.WriteLine("writing from main " + Demo.foo);
            th.Start();
            th.Join();
            Console.WriteLine("writing from main " + Demo.foo);
            Console.Read();
        }

        public static void ThreadFun( )
        {
            Console.WriteLine("writing from thread " + Demo.foo);
            Demo.foo= 500;
            Console.WriteLine("writing from thread " + Demo.foo);
        }

    }

    public class Demo
    {    
        [ThreadStatic]
        public static int foo = 100;               
    }

Output looks like below: 

You can see that main thread will get foo value as 100, but the next thread will gets its own seperate static varibale and the initial value as zero..........

*Note : I just tried the same attribute for non static fields, I can see that compiler wont give you any warnings/errors, but no impact.