Where to store data for current WCF call? Is ThreadStatic safe?

There’s a blog post which suggests implementing an IExtension<T>. You may also take a look at this discussion.

Here’s a suggested implementation:

public class WcfOperationContext : IExtension<OperationContext>
{
    private readonly IDictionary<string, object> items;

    private WcfOperationContext()
    {
        items = new Dictionary<string, object>();
    }

    public IDictionary<string, object> Items
    {
        get { return items; }
    }

    public static WcfOperationContext Current
    {
        get
        {
            WcfOperationContext context = OperationContext.Current.Extensions.Find<WcfOperationContext>();
            if (context == null)
            {
                context = new WcfOperationContext();
                OperationContext.Current.Extensions.Add(context);
            }
            return context;
        }
    }

    public void Attach(OperationContext owner) { }
    public void Detach(OperationContext owner) { }
}

Which you could use like that:

WcfOperationContext.Current.Items["user"] = _currentUser;
var user = WcfOperationContext.Current.Items["user"] as MyUser;