In LINQ to SQL, you can easily update data in a database by modifying any property of the object which is associated with Table<TEntity> collection and then call SubmitChanges() method. LINQ to SQL will translate your changes into the appropriate SQL UPDATE commands.
The following code updates the address of a customer whose first name is "Maria".
using (var db = new CustomerDataContext(@"Data Source=(localdb)\ProjectsV13;Initial Catalog=CustomerDB;"))
{
    var customer = db.Customers
        .Where(c => c.FirstName == "Maria")
        .FirstOrDefault();
    
    customer.Address = "Obere Street 59";
    
    db.SubmitChanges();
}