public async System.Threading.Tasks.Task TestAsAsync()
        {
            var asy = dict.AsAsync();

            Assert.NotNull(asy);
            Assert.Same(dict, asy);
            var key = "TestAsAsync";
            await asy.AddAsync(key, Model.CreateNew());

            Assert.True(dict.ContainsKey(key));
            dict.Remove(key);
        }