使用lambda聚合匿名类型

Question

I'm trying to print out a list of phone numbers (\\n for each number) in a format {type}:{number}. So from a list of 2 numbers I would print out:

 Home: 111-111-1111
 Cell: 222-222-2222

So far I can select into an anonymous type but when I go to aggregate it is leterally printing out the whole anonymous type on the screen looking exactly like below:

 new { phoneType = Home + ": ", phoneNumber = 111-111-1111 }

Should I even be using aggregate? This is what I'm working with:

  PhoneNumbers.Select(x => new { phoneType = x.PhoneType, phoneNumber = x.PhoneNumber1 }).Aggregate(
                (p, x) => new { phoneType = p.phoneType + ": ", x.phoneNumber });

Answer 1

If you just want the phone numbers as strings, you can create that string in a Select call:

var x = PhoneNumbers.Select(x => string.Format("{0}: {1}", x.PhoneType, x.PhoneNumber));

Your Aggregate call is basically a bug (assuming it even compiles) because you're combining the "current" phone number with the previous phone type. It's also unnecessary for combining the phone numbers as text because of existing string methods:

var phoneNumberStrings = PhoneNumbers.Select(x => string.Format("{0}: {1}", x.PhoneType, x.PhoneNumber));
var text = string.Join(Environment.NewLine, phoneNumberStrings);

Answer 2

While you could do this with IEnumerable<string>.Aggregate , I feel it's cleaner if you just use string.Join . Someone reading your code will be able to more easily get the meaning out if they see "join these strings with newline."

string.Join(
    Environment.NewLine,
    PhoneNumbers.Select(x =>
        string.Format("{0}: {1}", x.PhoneType, x.PhoneNumber));