为C＃中的每个表达式向lambda添加一个条件

Question

Basically I want to do this

foreach (var TA in TheToAddresses)
{
    if(TA.ToLower () != "a@a.com")
    {
        _message.ToRecipients.Add(TA);
    }
}

how do I modify this line to include the condition as well? Thanks

TheToAddresses.ForEach(TA => _message.ToRecipients.Add(TA));

Answer 1

TheToAddresses.ForEach(TA => 
{
  if(TA.ToLower () != "a@a.com")
     _message.ToRecipients.Add(TA) 
});

If ToRecipients is of type List you can write:

_message.ToRecipients.AddRange(TheToAddresses.Where(TA => TA.ToLower() != "a@a.com"));

Answer 2

You can write a multi-line lambda method by wrapping it with { }:

TheToAddresses.ForEach(TA =>
    {
        if(TA.ToLower () != "a@a.com")
        {
             _message.ToRecipients.Add(TA);
        }
     });

Answer 3

TheToAddresses.Where(r=> r.ToLower () != "a@a.com").ToList()
.ForEach(TA => _message.ToRecipients.Add(TA));

Answer 4

TheToAddresses.Where(address => address.ToLower() != "a@a.com").ToList().ForEach(TA => _message.ToRecipients.Add(TA));

Answer 5

TheToAddresses.Where(ta => ta.ToLower() != "a@a.com")
              .ForEach(TA => _message.ToRecipients.Add(TA));

Answer 6

What you wrote is nearly the right way. LINQ shouldn't have side-effects. See http://blogs.msdn.com/b/ericlippert/archive/2009/05/18/foreach-vs-foreach.aspx

foreach (var TA in TheToAddresses)
{
    if(!StringComparer.OrdinalIgnoreCase.Equals(TA, "a@a.com"))
    {
        _message.ToRecipients.Add(TA);
    }
}

The only point is that if you want to do case insensitive comparisons you don't ToLower() / ToUpper() (see http://blog.codinghorror.com/whats-wrong-with-turkey/ , beginning with Strings are where it really starts to get hairy )