title: Dynamically Assign Source column in import schema "expression" in Azure Data Factory using Lookup activity
body: <p>i am new in azure data factory V2</p>
  
  <p>i have schema file- </p>
  
  <blockquote>
    <p>CustomerSchema.csv</p>
  </blockquote>
  
  <p>Data-in CSV File</p>
  
  <pre><code>CustomerId, CustomerName, CustomerAddress
  </code></pre>
  
  <p>Actual Data File in CSV Formatoe
  FileName-CustomerMaster.CSV, data below</p>
  
  <pre><code>101,Aphilps,R-z1 west loan usa
  102,Jons s,202-3 sest road  london
  103,Ravi,Old Madaras banglore
  104,n Har,hi road -203 banglore
  105,Jons K,West-23-34 new york usa
  </code></pre>
  
  <p>Target File with Schema
  CustomerTraget.CSV</p>
  
  <p>CustomerId, CustomerName, CustomerAddress
  ----Blank no Data</p>
  
  <p>i have pipline where first activity is lookup activity that bring schema from file CustomerSchema.CSV</p>
  
  <p>output of lookup activity is correct, it's fetch 3 Columns name</p>
  
  <p><a href="https://i.stack.imgur.com/NrHrd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NrHrd.png" alt="enter image description here"></a> </p>
  
  <p>Now how i passed output of lookup activity in my copy activity import schema expression</p>
  
  <p>i have try below but not work</p>
  
  <p>@activity('ColumnLookup').output.firstRow in schema expression but it's not working</p>
  
  <p>please help me</p>