Updating Database using LINQ to SQL ?

Hello
i am trying to update a database records using DataContext and LINQ to SQl Classe ...
After adding the BibliothequeModel.dbml ...
i tried this code :
            BibliothequeModelDataContext ContextUpdate = new BibliothequeModelDataContext();
            var InfoDate = from i in ContextUpdate.Informations
                           where i.IDInfo == 1
                           select i;

            foreach (var item in InfoDate)
            {< ...