title: Aspose.Cells.CellsException - "You are using an evaluation copy and have opened files exceeding limitation"
body: <p>I have created a function that returns a <code>datatable</code> from a <code>workbook</code>.</p>
  
  <pre><code>public async Task&lt;DataTable&gt; GetDataTableFromTabRowColumn(string sheetName, int startRow, int endRow, int startCol, int endCol)
    {
       var task = new Task(() =&gt;
       {
          DataTable dt = new DataTable();
          Workbook wb = new Workbook(FilePath); // error line
          Worksheet worksheet = wb.Worksheets[sheetName];
  
          dt = worksheet.Cells.ExportDataTable(startRow - 1, startCol - 1, (endRow - startRow + 1), (endCol - startCol + 1), options);
       });
  
       task.Start();
       await task;
  
       return dt;
    }
  </code></pre>
  
  <p>It was running fine. When I made the function async, it's showing error:</p>
  
  <blockquote>
    <p>Aspose.Cells.CellsException: 'You are using an evaluation copy and
    have opened files exceeding limitation.'</p>
  </blockquote>
  
  <p>I am using licensed Aspose. Please help </p>