更新IList <T> 从另一个IList <T>

Question

I have two ILists.

users of type IList<CustomClassOne> and

contacts of type IList<CustomClassTwo> .

Both classes have a unique ID. I need fill CustomClassOne's property "Description" by using CustomClassTwo's property "Info".

foreach (CustomClassOne user in users )
{
    if (!string.IsNullOrEmpty(user.Description))
    {
        long id = user.ID;
        string desc = user.Description;

        var temp =  contacts.Select(p => p.ID = id);
        ...
        ...
    }
    else
        continue;

}

Answer 1

It sounds like you need to use a Join :

foreach (var pair in users.Join(contacts, u => u.ID, c => c.ID, Tuple.Create))
{
    pair.Item1.Description = pair.Item2.Info;
}

Or if you prefer query syntax :

var pairs = 
    from user in users 
    join contact in contacts on user.ID equals contact.ID
    select new { user, contact };
foreach (var pair in pairs)
{
    pair.user.Description = pair.contact.Info;
}

Answer 2

You can use a Join to match up the two types together, after which you can iterate the matches and apply the changes.

var query = from contact in contacts
    join user in users
    on contact.Id equals user.Id
    into users
    select new 
    {
        contact,
        users,
    }

foreach(var match in query)
    foreach(var user in match.users)
    {
        user.Description = match.contact.Info;
    }

Answer 3

You can make the search in a foreach loop and if found assign to the CustomClassOne instance:

foreach (CustomClassOne item in users)
{
     var temp = contacts.Find(c => c.ID == item.ID);
     item.Description = temp == null ? item.Description : temp.Info;
}