Overwrite Major Version Using Object Model

Question

I have versioning and checkin/checkout enabled in a SharePoint 2010 list, and for business-related reasons, would like to update information in a field: overwriting the field data for all versions in a similar manner and in place so that the version numbers do not change.

If I call SPListItemVersion.ListItem.UpdateOverwriteVersion(), it fails stating that I need to check out the item before making changes to it. Makes sense. So I precede the update statement with SPListItemVersion.ListItem.CheckOut() statement, attempt the update, and receive an error that I cannot overwrite a published version. I've also attempted to precede the check out with SPSite.AllowUnsafeUpdates = true, setting it back to false after the update call, but the latter error still occurs. Any ideas?

Stripped code below:

foreach (SPListItemVersion itemVersion in item.Versions){
  itemVersion.ListItem.File.CheckOut(SPFile.SPCheckOutType.Online, itemVersion.ListItem.File.TimeLastModified.ToString());
  site.AllowUnsafeUpdates = true;
  itemVersion.ListItem["FieldName"] = "changed value here";
  itemVersion.ListItem.UpdateOverwriteVersion();
  site.AllowUnsafeUpdates = false;
  itemVersion.ListItem.File.CheckIn("Updated list item version", SPCheckinType.OverwriteCheckIn);
}

Answer 1

To anyone that may find themselves facing this issue, you do not need to toggle the AllowUnsafeUpdates field. What worked for me is replacing the itemVersion.ListItem.UpdateOverwriteVersion() statement with itemVersion.ListItem.SystemUpdate(false). The parameter passed in tells SharePoint to not create a new version when updating.

Edit: This answer only updates the current item again. SPListItemVersion field references are available via a get only; it appears this is not possible in the object model.