DocumentDB Inconsistent Update Behavior

In the following code, inputs performed to the input binding are persisted, but the same updates performed to the dynamically bound instance are not persisted:

public static async Task Run(string input, Binder binder, JObject item, TraceWriter log)
{
    JObject document = await binder.BindAsync<JObject>(
new DocumentDBAttribute("ItemDb", "ItemCollection")
    {
        ConnectionStringSetting = "mathewctest_DOCUMENTDB",
        Id = "c31d48aa-d74b-46a3-8ba6-0d4c6f288559"
    });

    log.Info("Item before: " +  document.ToString());
    document["text"] = "Modified!";

    log.Info("Item before: " +  item.ToString());
    item["text"] = "Modified!";
}

The expectation is that these two codepaths behave the same. See SO issue here: http://stackoverflow.com/questions/42007289/azure-functions-update-documentdb-document-with-binder.

[TheeJamesLee]

@brettsam so, does this mean this this section in the docs is wrong?

https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-documentdb#input-sample-in-c

// Change input document contents using DocumentDB API input binding 
public static void Run(string myQueueItem, dynamic inputDocument)
{   
  inputDocument.text = "This has changed.";
}

[brettsam]

Wouldn’t it affect everyone using Node with these bindings? People may be persisting these changes themselves today. A change here would auto-persist them as well.