public async Task AllocateIdAsync()
{
string projectId = _fixture.ProjectId;
string namespaceId = _fixture.NamespaceId;
// Snippet: AllocateIdAsync
DatastoreDb db = DatastoreDb.Create(projectId, namespaceId);
KeyFactory keyFactory = db.CreateKeyFactory("message");
Key key = await db.AllocateIdAsync(keyFactory.CreateIncompleteKey());
// End snippet
}