I'm assuming that, by "total row count," you mean the total number of rows across all pages of the grid.

The best approach is to get the total number of rows on the server, by retrieving the number from the data source you'll bind to WebGrid.  You can store that result in a hidden field, so that the number is available on the client.

WebGrid has no functionality itself to get a "total" row count through client-side code.