private void UpdatePrice(DevExpress.XtraGrid.Views.Base.ColumnView View) {
   // Obtain the Price column.
   DevExpress.XtraGrid.Columns.GridColumn col = View.Columns.ColumnByFieldName("Price");
   if (col == null) return;
   View.BeginSort();
   try {
      // Obtain the number of data rows.
      int dataRowCount = View.DataRowCount;
      // Traverse data rows and change the Price field values.
      for (int i = 0; i < dataRowCount; i++) {
         object cellValue = View.GetRowCellValue(i, col);
         double newValue = Convert.ToDouble(cellValue) * 0.9;
         View.SetRowCellValue(i, col, newValue);
      }
   } finally { View.EndSort(); }
}

Private Sub UpdatePrice(ByVal View As DevExpress.XtraGrid.Views.Base.ColumnView)
   ' Obtain the Price column.
   Dim Col As DevExpress.XtraGrid.Columns.GridColumn = View.Columns.ColumnByFieldName("Price")
   If Col Is Nothing Then Exit Sub
   View.BeginSort()
   Try
      ' Obtain the number of data rows.
      Dim DataRowCount As Integer = View.DataRowCount
      ' Traverse data rows and change the Price field values.
      Dim I As Integer
      For I = 0 To DataRowCount - 1
         Dim CellValue As Object = View.GetRowCellValue(I, Col)
         Dim NewValue As Double = Convert.ToDouble(CellValue) * 0.9
         View.SetRowCellValue(I, Col, NewValue)
      Next
   Finally
      View.EndSort()
   End Try
End Sub

int currentRowHandle = gridView1.GetVisibleRowHandle(0);
while(currentRowHandle != DevExpress.XtraGrid.GridControl.InvalidRowHandle) {
   // place any code for row processing here
   // ...
   currentRowHandle = gridView1.GetNextVisibleRow(currentRowHandle);
}

Dim CurrentRowHandle As Integer = GridView1.GetVisibleRowHandle(0)
While currentRowHandle <> DevExpress.XtraGrid.GridControl.InvalidRowHandle
   ' place any code for row processing here
   ' ...
   CurrentRowHandle = GridView1.GetNextVisibleRow(CurrentRowHandle)
End While