Exception iterating over a DataStructures dictionary

Exception - Newtonsoft.Json.JsonSerializationException, Could not create an instance of type System.Collections.Generic.IEnumerator`1[System.Collections.Generic.KeyValuePair`2[System.String,TestCouchbaseCollection.Foo]]. Type is an interface or abstract class and cannot be instantiated. Path 'Fred', line 1, position 8.

using (var cluster = await Cluster.ConnectAsync("couchbase://dev-docker01", "Administrator", "password"))

{

	var bucket = await cluster.BucketAsync("sms-data").ConfigureAwait(false);

	var collection = await bucket.DefaultCollectionAsync().ConfigureAwait(false);

	var dict = collection.Dictionary<Foo>("testdatadict");

	await dict.ClearAsync().ConfigureAwait(false);

	await dict.AddAsync("Fred", new Foo { Name = "Tom", Age = 50 });

	await dict.AddAsync("Bill", new Foo { Name = "Dick", Age = 30 });

	foreach (var item in dict)

	{

		Console.WriteLine($"{item.Key} - {item.Value.Name}, {item.Value.Age}");

	}

}