title: Azure Data Factory Data flow expression builder using parameters
body: <p>I am trying to pass pipeline parameter to Data flow activity while I try to pass the value for my directory/folder. As <code>concat('myArchive/', $myFolderDF)</code> gives me the error: <code>Column operands are not allowed in literal expressions</code>. I tried using this <code>'{$myFolderDF}'</code> and still get the error. Could you please guide me on using parameters in expressions in Data flow activity.</p>
  <p><em><strong>JSON:</strong></em></p>
  <pre><code>parameters{
      myFolderDF as string
  }
  source(allowSchemaDrift: true,
      validateSchema: false,
      ignoreNoFilesFound: false,
      format: 'csv',
      fileSystem: 'FileSource',
      folderPath: (concat('myFileArchive/',$myFolderDF)),
      fileName: (concat(lower($myFolderDF),'.csv')),
      documentForm: 'documentPerLine') ~&gt; DFSource
  DFSource sink(allowSchemaDrift: true,
      validateSchema: false,
      format: 'csv',
      fileSystem: 'FileArchive',
      folderPath: (concat('myFileArchive/',$myFolderDF)),
      partitionFileNames:[(concat($myFolderDF,toString(currentTimestamp(),'MMddyyyy'),'.csv'))],
      umask: 0022,
      preCommands: [],
      postCommands: [],
      skipDuplicateMapInputs: true,
      skipDuplicateMapOutputs: true,
      saveOrder: 0,
      partitionBy('hash', 1)) ~&gt; DFFileArchive
  </code></pre>
  <p><a href="https://i.stack.imgur.com/LRwod.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LRwod.jpg" alt="PipelineParameter" /></a></p>
  <p><a href="https://i.stack.imgur.com/iVaMR.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iVaMR.jpg" alt="DataflowParameter" /></a></p>