Problem with converting int to string in Linq to entities

Use LinqToObject : contacts.AsEnumerable()

var items = from c in contacts.AsEnumerable()
            select new ListItem
            {
                Value = c.ContactId.ToString(),
                Text = c.Name
            };

I solved a similar problem by placing the conversion of the integer to string out of the query. This can be achieved by putting the query into an object.

var items = from c in contacts
            select new 
            {
                Value = c.ContactId,
                Text = c.Name
            };
var itemList = new SelectList();
foreach (var item in items)
{
    itemList.Add(new SelectListItem{ Value = item.ContactId, Text = item.Name });
}

With EF v4 you can use SqlFunctions.StringConvert. There is no overload for int so you need to cast to a double or a decimal. Your code ends up looking like this:

var items = from c in contacts
            select new ListItem
            {
                Value = SqlFunctions.StringConvert((double)c.ContactId).Trim(),
                Text = c.Name
            };