concat linq查询结果为字符串？

Question

I have this simple class :

class A
{
  public string Name { get; set; }
  public int Age { get; set; }
}

And I have a dictionary :

Dictionary<string,A> dic = new Dictionary<string,A>();

dic["a"]=new A(){ Age=2, Name="aa"};
dic["b"]=new A(){ Age=3, Name="baa"};
dic["c"]=new A(){ Age=4, Name="caa"};

And here I see all the items in a visible way :

Console.WriteLine (dic.Select(f=>f.Key+" =>"+f.Value.Age+" "+f.Value.Name));

output :

a  =>2      aa  
b  =>3      baa  
c  =>4      caa 

but I want it to be as a string !

something like this string value :

@"a  =>2      aa  \n
  b  =>3      baa  \n
  c  =>4      caa ";

I could do it with ToArray and string.join :

var t=dic.Select(f=>f.Key+"  =>"+f.Value.Age+"      "+f.Value.Name);
Console.WriteLine (String.Join("\n",t.ToArray() ));

But I'm sure there is a better ( shorter , elegant) way using this statement : (with a bit of addition)

dic.Select(f=>f.Key+" =>"+f.Value.Age+" "+f.Value.Name)

Any help ?

Answer 1

You can use Aggregate Extension Method

string s = dic.Aggregate(String.Empty, 
                         (current, f) => 
                         String.Format("{0}\n{1} => {2} {3}", 
                                       current, 
                                       f.Key, 
                                       f.Value.Age,
                                       f.Value.Name))
              .TrimStart();

Or by using a StringBuilder

string s = dic.Aggregate(new StringBuilder(), 
                         (current, f) => 
                         current.AppendLine(
                             String.Format("{0} => {1} {2}", 
                                 f.Key, 
                                 f.Value.Age,
                                 f.Value.Name))
              .ToString();

Answer 2

You solution is fine, the only thing I would get rid of is the call to ToArray , so

Console.WriteLine (String.Join("\n",t ));

or

Console.WriteLine (String.Join(Environment.NewLine, t));