title: Azure data factory dataflow not present null values in JSON format
body: <p>I am looking for how to present my null values with the Azure Data Factory Dataflow activity. 
  Currently, I am using standard dataflow for modelling my data from Azure SQL database and drag it into Blob storage in JSON format. 
  <a href="https://i.stack.imgur.com/ZdKMo.png" rel="nofollow noreferrer">But if the dataset source has a null value, the column in the row is skipped in JSON</a>. </p>
  
  <p>UPDATE:
  <a href="https://i.stack.imgur.com/I8iPQ.png" rel="nofollow noreferrer">Here is the results of having data, having entry string as data and null value</a>.</p>
  
  <p>Please, give me some advice on how to proceed, in order to resolve the problem. With Copy activity I don't have the same issue - null values are presented with ""</p>
  
  <p>Thanks in advice!
  Cheers,
  Vesela</p>