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To prevent rows from becoming unshared, use the following guidelines:

         Avoid indexing the Rows collection or iterating through it with a foreach loop. You will not typically need to access rows directly. DataGridView methods that operate on rows take row index arguments rather than row instances. Additionally, handlers for row-related events receive event argument objects with row properties that you can use to manipulate rows without causing them to become unshared.

         If you need to access a row object, use the DataGridViewRowCollection.SharedRow(Int) method and pass in the row's actual index. Note, however, that modifying a shared row object retrieved through this method will modify all the rows that share this object. The row for new records is not shared with other rows, however, so it will not be affected when you modify any other row. Note also that different rows represented by a shared row may have different shortcut menus. To retrieve the correct shortcut menu from a shared row instance, use the GetContextMenuStrip method and pass in the row's actual index. If you access the shared row's ContextMenuStrip property instead, it will use the shared row index of -1 and will not retrieve the correct shortcut menu.

         Avoid indexing the DataGridViewRow.Cells collection. Accessing a cell directly will cause its parent row to become unshared, instantiating a new DataGridViewRow. Handlers for cell-related events receive event argument objects with cell properties that you can use to manipulate cells without causing rows to become unshared. You can also use the CurrentCellAddress property to retrieve the row and column indexes of the current cell without accessing the cell directly.

         Avoid cell-based selection modes. These modes cause rows to become unshared. Instead, set the SelectionMode property to DataGridViewSelectionMode.FullRowSelect or DataGridViewSelectionMode.FullColumnSelect.

         Do not handle the DataGridViewRowCollection.CollectionChanged or RowStateChanged events. These events cause rows to become unshared. Also, do not call the DataGridViewRowCollection.OnCollectionChanged(CollectionChangeEventArgs) or OnRowStateChanged(Int,DataGridViewRowStateChangedEventArgs) methods, which raise these events.

         Do not access the SelectedCells collection when the SelectionMode property value is FullColumnSelect, ColumnHeaderSelect, FullRowSelect, or RowHeaderSelect. This causes all selected rows to become unshared.

         Do not call the AreAllCellsSelected(boolean) method. This method can cause rows to become unshared.

         Do not call the SelectAll method when the SelectionMode property value is CellSelect. This causes all rows to become unshared.

         Do not set the ReadOnly or Selected property of a cell to false when the corresponding property in its column is set to true. This causes all rows to become unshared.

         Do not access the DataGridViewRowCollection.List property. This causes all rows to become unshared.

• Do not call the Sort(IComparer) overload of the Sort method. Sorting with a custom comparer causes all rows to become unshared.