Rowfilter with multiple textboxes

The DataView.RowFilter property uses special syntax rather than ordinary SQL. It's described in the MSDN docs for the DataColumn.Expression property which uses the same syntax:

http://msdn.microsoft.com/en-us/library/system.data.datacolumn.expression.aspx

So, I'd try here:

view.RowFilter = String.Format("BattingAverage >= {0} AND BattingAverage <= {1}", minimum, maximum);