title: Evaluate DataTable Expression
body: <p>I have a DataTable which is built from reading an Excel file (using OLEDB connection).  I would like to add a column which contains a comma separated list of the values in all the columns.</p>
  
  <p>So if I have FirstName, LastName, Address then I want a 4th column which is a comma-separated concatenation of FirstName, LastName and Address.  I would rather not iterate over the records, because there could be 100,000's to 1,000,000's of records.  Is there a way to do this in the SQL statement?  I have <code>"select * from [" + sheetName[i] + "]"</code> where <code>sheetName[i]</code> is the current sheet name of the current loop (looping over X number of sheets).</p>
  
  <p>In the end I am building a completely different DataTable containing columns in which I will be using to do SqlBulkCopy to a table in my SQL Server database. I added columns I needed for this bulk copy and then Merged my datatable from the Excel sheet to the end of my newly created DataTable.  Then I added a new column where I used. Expression to comma-separate my fields from Excel sheet datatable.  However, my new DataTable must be in exact form as the table i am doing bulk copy into.  So I want to delete the columns not in my SQL table, but I get error (which makes sense) when I try to delete these columns since they are a part of the Expression for one of the other columns.</p>
  
  <p>So, is there a way to either query the Excel file to concatenate a comma-separated new column?  Or to force evaluation on the datatable Expression so that it evaluates the expression and stores the evaluated string to that column rather than using the Expression solely?</p>