title: Use LINQ to get datatable row numbers meeting certain conditions
body: <p>How can I get an array of datatable row numbers which meet a certain criteria?  For example I have a datatable with a column "DateTime".  I want to retrieve the row numbers of the datatable where "DateTime" equals the variable startTime.</p>
  
  <p>I know how to retrieve the actual row, but not the number of the row in the datatable.</p>
  
  <p>Any help will be appreciated :)</p>