while (ItemsCompleted < PayloadItems.Count) {
    do {
            NextSource();
    } while (ItemsCompleted < PayloadItems.Count && ItemCompletionRegister[Index]);
    Debug.Print(DebugUtility.CreateReportString("PayloadMux", "Execute", "Selected stream",
            Index));
    ExecuteOperation();
}

protected override sealed void NextSource()
{
    Index = EntropySource.NextPositive(0, PayloadItems.Count - 1);
    Debug.Print(DebugUtility.CreateReportString("SimplePayloadMux", "NextSource", "Generated index",
        Index));
}