title: ssis add column with default value if not present in source file
body: <p>i am making an SSIS package in which I transfer several Excel files in a unique Excel file.</p>
  
  <p>The problem is that the input files may have different structures (some colulns might not be present).</p>
  
  <p>my SSIS structure is like this one :</p>
  
  <ol>
  <li>a foreach container that take each file one by one</li>
  <li>A Script that shows a windowsform that allow me to enter the default values for my columns in Variables</li>
  <li>my dataflow task</li>
  </ol>
  
  <p>In My dataflow task, i'd like to take the values from the Excel file and put them to the destination file.
  If the column does not exist, i want the dataflow to make a new column using the default value.</p>
  
  <p>I managed to do it but I have a problem with the "if the column does not exist" thing. I added column with a Derived Column but how can he first check if the column does not exists in the Source File. i don't want to put default value each time. if the column is present i want to use it instead of a default value.</p>
  
  <p>Thanks for your answers,</p>