regarding [ThreadStatic()] c#

[ThreadStatic()]是什么意思

我得到了一段代码，我找到了[ThreadStatic()]在那里使用它是什么意思....何时使用[ThreadStatic()]

public class Context
{
[ThreadStatic()]
private static Context _Context = null;
private HttpContext _HttpContext = null;
public Context()
{
    _HttpContext = HttpContext.Current;
}
public static Context Current
{
    if(_Context == null || 
       _HttpContext != _HttpContext.Current)
    {
        _Context = new Context();
    }
    return _Context;
}
}