DataTable seemes still has data after reset. I do somethig like:
DataTable myTable = new DataTable();
myTable.Columns.Add("myColumn");
myTable.Columns["myColumn"].DataType = typeof(double);
DataRow myRow = myTable.NewRow();
myTable.Reset();
myTable.Columns.Add("myColumn");
myTable.Columns["myColumn"].DataType = typeof(double);
and get exception "Cannot change DataType of a column once it has data", though .Reset method was called.