<p>I have two DataTables, <code>A</code> and <code>B</code>, produced from CSV files.  I need to be able to check which rows exist in <code>B</code> that do not exist in <code>A</code>.</p>

<p>Is there a way to do some sort of query to show the different rows or would I have to iterate through each row on each DataTable to check if they are the same?  The latter option seems to be very intensive if the tables become large.</p>

You can use the Merge and GetChanges methods on the DataTable to do this:
```
```
A.Merge(B); // this will add to A any records that are in B but not A
return A.GetChanges(); // returns records originally only in B
```
```