How can a readonly static field be null?

Question

So here\'s an excerpt from one of my classes:

    [ThreadStatic]
    readonly static private AccountManager _instance = new AccountManager();

    private Ac         


        

Answer 1

This is a confusing part of the ThreadStatic attribute. Even though it creates a value per thread, the initalization code is only run on one of the threads. All of the other threads which access this value will get the default for that type instead of the result of the initialization code.

Instead of value initialization, wrap it in a property that does the initialization for you.

[ThreadStatic]
readonly static private AccountManager _instance;

private AccountManager()
{
}

static public AccountManager Instance
{
  get 
  { 
    if ( _instance == null ) _instance = new AccountManager();
    return _instance; 
  }
}

Because the value _instance is unique per thread, no locking is necessary in the property and it can be treated like any other lazily initialized value.