title: Azure Data Factory Array of Strings mapped in Copy Activity, Cosmos SQL sink only accepts string and not array of strings?
body: <p>I have an Azure Data Factory Pipeline with a Copy Activity. Source is a JSON file (some generated pipeline variables too) and Sink is a Cosmos SQL Collection. Before Mapping I imported the schema and a particular field from the sink collection has been identified to be of type array [] with string elements.</p>
  <p>The problem however is that this field mapping now only accepts a STRING and not an Array of strings. I am not sure if this a bug with ADF or something to do with how I genrated the source variable for this mapping.</p>
  <p><a href="https://i.stack.imgur.com/Z83TN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Z83TN.png" alt="enter image description here" /></a></p>
  <p>If the source variable accessGroups is of string the copy works fine(it shouldn't though right???). However if I substitute this with a variable containing an array of strings I get the following error:</p>
  <p><strong>Failed to convert the value in 'value' property to 'System.String' type. Please make sure the payload structure and value are correct. Object must implement IConvertible.</strong></p>
  <p>Just to be clear, I am mapping the source variable accessGroups to ['accessGroups'] and not ['accessGroups'][0]. Besides ADF does not allow mapping source variables to individual array elements anyway.</p>
  <p>Any one faced this issue before or aware of any workaround?</p>