convert foreach with looping into Linq statement

foreach (Contact contactValues in contactsFromDb)
                {
                    Outlook.MAPIFolder contacts = Globals.ThisAddIn.Application.Session.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderContacts);
                    Outlook.Items colItems = contacts.Items;
                    string contactId = contactValues.Id.ToString();
                    string FilterString = "[CustomerID] = '" + contactId + "'";
                    Outlook.ContactItem excistingContact = (Outlook.ContactItem)colItems.Find(FilterString);
                    if (excistingContact == null)
                    {
                        Outlook.ContactItem oContact = (Outlook.ContactItem)contacts.Items.Add(Common.Helper.ContactClassForm);
                        AssignvaluesToContact(contactValues, null, contacts);
                        i++;
                    }
                    else
                    {
                        if (excistingContact.LastModificationTime < contactValues.LastModifiedDate)
                        {
                            Outlook.ContactItem oContact = (Outlook.ContactItem)contacts.Items.Add(Common.Helper.ContactClassForm);
                            AssignvaluesToContact(contactValues, excistingContact, contacts);
                        }
                    }
                }