How to Construct the Email To activity in SharePoint 2013 Workflow

Question

I have a created a custom workflow and custom association and initiation form using SharePoint 2013.
My Assn. form is fine.  I pass in the people picker (Active Directory group) value to my workflow just fine.
Now on my Init form I use the passed in value from people picker and display a list of users and email addresses from the people picker group.  The list of users and email addresses are listed in a table with a check box to the left of each row. I am
using JQuery, Knockout and MVC web service to retrieve the values from the group.
All is well.
Now my users pick who they want to send the email to.  Let's say they pick two users!
When the user clicks the submit button, I have JSOM code which starts the workflow and sends in the 2 users email addresses as an argument to theworkflow.
 Note:  I tried sending my two emails as a collection and failed.  So i converted it to a string.  The variable is called strUsers.
Since the argument is a string and Email Activity requires the To attribute to be an array, I use the BuildCollection<String> Activity to convert my string to an array.
Now in my workflow I use WriteToHistory Activity to write out my BuildCollection variable (recipients).  Here's what is sent to the workflow history... [email protected];joejones@yahoo,com)  Note:
 Both names are bogus and I'm not Joe Jones.
I then configure the email Activity and set to To property to my BuildActivity variable (recipients).
When I deploy my Visual Studio 2013 solution, and attach my workflow to a publishing page, I am getting this error after I submit the Init form.
An unhandled exception occurred during the execution of workflow instance.  System.ArgumentNullException.
Does anyone know of an example of how to set up the Email To collection value.
Note:  I tried using comma and semi-colon for my string (strUsers).  Neither worked.
Thanks
Tom
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Answer 1

I think I'm getting close.
Here’s an
article
that helped me out and below is my code.  Note:  I added a ParseDynamicValue and GetDynamicValueProperty to push the data from the "emails" property to colleciton of strings called EmailCollect.
Here is what the data look likes
The value of Selected Emails is [{"emails":"[email protected]"},{"emails":"[email protected]"}]
 Code excerpt in InitiationForm.  Note:  I am using MVVM and Knockout for the selected users from a list with checkboxes.
                //build array for workflow 
              var emailUsers =
new Array();
                //cycle through viewmodel emails
for (var
i = 0; i < viewModel.SelectedEmails().length; i++)
var a =
new Object();
                    a["emails"]
= viewModel.SelectedEmails()[i];
                    emailUsers.push(a);
wfParams['strSelectedEmailsHMgr']
= JSON.stringify(emailUsers);
                 // Get workflow subscription
and then start the workflow
var context = SP.ClientContext.get_current();
var wfManager = SP.WorkflowServices.WorkflowServicesManager.newObject(context, context.get_web());
var wfDeployService = wfManager.getWorkflowDeploymentService();
var subscriptionService = wfManager.getWorkflowSubscriptionService();
                context.load(subscriptionService);
                context.executeQueryAsync(
function (sender, args) {
// Success
var subscription =
null;
// Load the workflow subscription
if (subscriptionId)
                            subscription = subscriptionService.getSubscription(subscriptionId);
if (subscription) {
if (itemId !=
null && itemId !=
// Start list workflow
                                wfManager.getWorkflowInstanceService().startWorkflowOnListItem(subscription,
itemId, wfParams);
Now I deploy and publish the workflow but now I’m getting this error when trying to 
System.InvalidOperationException: Looking up a value using a key is not supported on an instance of 'Microsoft.Activities.Dynamic.DynamicJsonArray'. at Microsoft.Activities.Dynamic.DynamicItem.TryGetValue(String
key, DynamicItem& value) at Microsoft.Activities.Dynamic.DynamicValueBuilder.PathSegmentFactory.ObjectPathSegment.Get(DynamicItem obj) at Microsoft.Activities.GetDynamicValueProperty`1.Execute(CodeActivityContext context) at System.Activities.CodeActivity`1.InternalExecute(ActivityInstance
instance, ActivityExecutor executor, BookmarkManager bookmarkManager) at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)
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