How to edit / update / change "Read Only" list columns

We had to retrieve data from our archive storage, back to the sharepoint sites. The problem was that when we retrieved the data back to the sharepoint doclib\lists we changed the Meta Data of our items ( such as Modified, Modified By ) which most of them appear as "read only" columns.

The solution - We had to interfere in our lists, and touch those "read only" columns \ Fields. Remembering we had to avoid changing those lists\Doclibs columns and keep the "old" metadata ( before the retrieval process ).

Code Snippet for how changing the data in the "read only" column such as "Modified" -

 

SPFieldCollection colFields = list.Fields;
            for (int i = 0; i < colFields.Count; i++)
            {
                SPField field = colFields[i];
                try
                {

                    if (list.Fields[i].Title == "Modified")
                    {
                        if (field.ReadOnlyField)
                        {
                            list.Fields[i].ReadOnlyField = false;
                            for (int j = 0; j < list.Items.Count; j++)
                            {
                                SPListItem oListItem = list.Items[j];
                                DateTime date = (DateTime)oListItem[list.Fields[i].Title];

                                // updating the relvant stuff on that item.

                                oListItem[list.Fields[i].Title] = date;
                                oListItem.Update();

                            }
                        }
                    }
                }
                catch(Exception e)
                {
                    Console.WriteLine(e.ToString());
                }
            }

You can play with it more, and adjust it. Hope you got the idea.

Good luck.