Question

I have a struct Test, which I add as a value to a dictionary.
What I want to do is sort the dictionary by the DateTime of the value.

    struct Test
    {
        DateTime dt;
        public string ID;
    }

    Dictionary<String, Test> dict = new Dictionary<String,Test>();
    Test t = new Test();

    t.dt = DateTime.Now;
    t.ID = "XUDF";
    dict.Add(t.ID, t);

    t.dt = DateTime.Now.AddDays(17);
    t.ID = "RFGT";
    dict.Add(t.ID, t);

    t.dt = DateTime.Now.AddDays(3);
    t.ID = "ADLV";
    dict.Add(t.ID, t);

    t.dt = DateTime.Now.AddHours(2);
    t.ID = "SKFU";
    dict.Add(t.ID, t);

I’m not sure what to do after this.
Also, is this the best way to go about it?
I’m using .net 3

What I am trying to do is have a list that I can access by the ID but also ordered by the datetime in t.dt.
I want to be able to select an object by its ID but also be able to iterate through and have it come out in order of datetime.

Answer 1

What do you mean by “sort the dictionary”? A dictionary has no “order” to it per se. It’s a keyed collection, the underlying implementation of which is a hash table.

I assume what you meant to say is, “I want to enumerate over the contents of the dictionary in order of the values.” That can be done thusly:

public void List( Dictionary<string,DateTime> dict )
{
  int i = 0 ;
  foreach( KeyValuePair<string,DateTime> entry in dict.OrderBy( x => x.Value ).ThenByDescending( x => x.Key ) )
  {
    Console.WriteLine( "{0}. Key={1}, Value={2}" , ++i , entry.Key , entry.Value ) ;
  }
  Console.WriteLine( "The dictionary contained a total of {0} entries." , i ) ;
}

If on the other hand, you actually want/need an ordered collection, you need to spec out what your actual requirements are.