Thanks. I almost there. it works with one selection but when I select multiple items i get the following error.
SeverException was handeled by user code.
Item does not exist. It may have been deleted by another user.
Highlighted in green was clientContext.ExecuteQuery. I think it had to do with incorrect query with multiple values. I believe my code is formed wrong or wrong syntax.
here is my code.
//update list item
string siteUrl = http://sp-app/dev;
ClientContext clientContext = new ClientContext(siteUrl);
list oList = clientContext.Web.Lists.GetByTitle("Item Inventory");
PathNavigator root = MainDataSource.CreateNavigator();
XPathNodeIterator iter = root.Select("/my:myFields/my:group1", NamespaceManager);
while (iter.MoveNext())
{
string value = iter.Current.Value;
int id;
Int32.TryParse(value, out id);
ListItem oListItem = oList.GetItemById(id);
oListItem[
"Title"] = field1;
oListItem.Update();
clientContext.ExecuteQuery();