The following code is excerpted from the (Windows Identity Foundation SDK) template that MS uses to create a new Security Token Service Web Site.

public static CustomSecurityTokenServiceConfiguration Current
{
get
{
HttpApplicationState httpAppState = HttpContext.Current.Application;
CustomSecurityTokenServiceConfiguration customConfiguration = httpAppState.Get( CustomSecurityTokenServiceConfigurationKey ) as CustomSecurityTokenServiceConfiguration;
if ( customConfiguration == null )
{
lock ( syncRoot )
{
customConfiguration = httpAppState.Get( CustomSecurityTokenServiceConfigurationKey ) as CustomSecurityTokenServiceConfiguration;
if ( customConfiguration == null )
{
customConfiguration = new CustomSecurityTokenServiceConfiguration();
httpAppState.Add( CustomSecurityTokenServiceConfigurationKey, customConfiguration );
}
}
}
return customConfiguration;
}
}

I'm relatively new to multi-threaded programming. I assume that the reason for the lock statement is to make this code thread-safe in the event that two web requests arrive at the web site at the same time.

However, I would have thought that using lock (syncRoot) would not make sense because syncRoot refers to the current instance that this method is operating on... but this is a static method?

How does this make sense?