title: Azure Data Factory V2 Copy Activity file filters
body: <p>I am using Data Factory v2 and I currently have a simple copy activity which copies files from an FTP server to blob storage. The file names on this server are of the following form :</p>
  
  <pre><code>File_{Year}{Month}{Day}.zip
  </code></pre>
  
  <p>In order to download the most recent file I add this filter to my input dataset json file :</p>
  
  <pre><code>"fileName": {
      "value": "@concat('File_',formatDateTime(utcnow(), 'yyyyMMdd'), '.zip')",
      "type": "Expression"
  }
  </code></pre>
  
  <p>I now want to be able to download yesterday's file which is possible using <code>adddays()</code>.</p>
  
  <p>However I would like to be able to do this in the same copy activity and it seems that Data Factory v2 does not allow me to use the following kind of regular expression logic :</p>
  
  <pre><code>@concat('File_',formatDateTime(utcnow(), 'yyyyMMdd'), '.zip') || @concat('File_', formatDateTime(adddays(utcnow(), -1), 'yyyyMMdd'), '.zip')
  </code></pre>
  
  <p>Is this possible or do I need a separate activity ?</p>
  
  <p>It would seem strange to need a second activity since a Copy Activity can only take a single input but if the regex is simple enough, then multiple files are treated as a single input and if not then multiple files are treated as multiple inputs.</p>