Event Receiver trouble in permission changed

Question

I have the following problem with this code:

    public override void ItemUpdating(SPItemEventProperties properties)
    {
        base.ItemUpdating(properties);

        const string fieldInternalNameWrt = "UserWrt";
        const string fieldInternalNameRdr = "UserRdr";

        SPListItem item = properties.ListItem;
        SPUser userWrt = null;
        SPUser userRdr = null;

        if (properties.AfterProperties[fieldInternalNameWrt] != null)
        {
            string userValueWrt = properties.AfterProperties[fieldInternalWrt].ToString();
            userWrt = GetSPUserFromId(properties.ListTitle, userValueWrt, fieldInternalWrt, properties);
        }

        if (properties.AfterProperties[fieldInternalNameRdr] != null)
        {
            string userValueRdr = properties.AfterProperties[fieldInternalNameRdr].ToString();
            userRdr = GetSPUserFromId(properties.ListTitle, userValueRdr, fieldInternalNameRdr, properties);
        }

        if (userWrt == null && userRdr == null)
            return;

        SPRoleAssignment roleAssignmentWrt = null;
        if (userWrt != null)
        {
            roleAssignmentWrt = new SPRoleAssignment(userWrt);
            var roleDefinition = properties.Web.RoleDefinitions.GetByType(SPRoleType.Contributor);
            roleAssignmentWrt.RoleDefinitionBindings.Add(roleDefinition);
        }

        SPRoleAssignment roleAssignmentRdr = null;
        if (userRdr != null)
        {
            roleAssignmentRdr = new SPRoleAssignment(userRdr);
            var roleDefinition = properties.Web.RoleDefinitions.GetByType(SPRoleType.Reader);
            roleAssignmentRdr.RoleDefinitionBindings.Add(roleDefinition);
        }

        try
        {
            this.EventFiringEnabled = false;

            lock (_thisLock)
            {
                SPSecurity.RunWithElevatedPrivileges(() =>
                {
                    item.BreakRoleInheritance(false);

                    foreach (SPRoleAssignment assignment in item.RoleAssignments)
                    {
                        assignment.RoleDefinitionBindings.RemoveAll();
                        assignment.Update();
                    }

                    if (roleAssignmentWrt != null)
                        item.RoleAssignments.Add(roleAssignmentWrt);

                    if (roleAssignmentRdr != null)
                        item.RoleAssignments.Add(roleAssignmentRdr);

                    item.Update();
                });
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            this.EventFiringEnabled = true;
        }
    }

    public static SPUser GetSPUserFromId(string listName, string currentValue, string nameField, SPItemEventProperties properties)
    {
        SPFieldUserValue fieldValue;

        using (SPWeb web = properties.OpenWeb())
        {
            var userField = (SPFieldUser)web.Lists[listName].Fields.GetField(nameField);
            fieldValue = (SPFieldUserValue)userField.GetFieldValue(currentValue);
        }

        return fieldValue.User;
    }

the item's permissions was changed but I receive the following error!

http://i.stack.imgur.com/l1lgn.jpg1

anyone knows why?

Answer 1

A couple of comments:

• As @AndersRask mentioned in the comment put the restore of EventFiringEnabled in a finally block
• Your current use of SPSecurity.RunWithElevatedPrivileges isn't doing anything except wasting resources. In order for it to allow more than the current user you need to allocate a new SPSite + SPWeb + SPList + SPListItem
• My guess is that the lock also is completely useless
• You should use SPListItem.SystemUpdate when doing changes behind the users back
• If you don't want us to see the name of the document and user then you should also strike it out in the blue band

Answer 2

I had similar issue with ItemUpdating recently. When trying to update field in an updating item I had the same exception as yours. My solution was to change event receiver from ItemUpdating to ItemUpdated. If you need strictly ItemUpdating event then I suggest to run code which refers to item modification in a separate thread.

Of course such solution have less control over item behavior and may lead to concurrent update issues.

Answer 3

How Per wrote you, you don't need the SPSecurity.RunWithElevatedPrivileges and a lock on you code. I think you don't need a item.Update or SystemUpdate because you are in updateing. If the document it's new you have the error because sharepoint doesn't find it.

Try to remove all the code that the guys are suggest to you and move the base.ItemUpdating(properties); at the end of function an remove item.Update() method.