How to add items in dictionary in which value is list of class?

Question

I am having a below dictionary :

Dictionary<string, List<Coordinates>> Coordinates = new Dictionary<string,List<Coordinates>>();

 public class Coordinates
    {
        public int Id { get; set; }
        public decimal range { get; set; }
        //other properties
    }

Now I am trying to add coordinates to my dictionary for specific region id and if same coordinates id comes then I don't want to add it.

Below is my web service method:

public string MyMethod(string coordinateId, string regionId)
        { 
           var coordinates = Coordinates.Where(ed => (ed.Key == regionId)).SelectMany(ed => ed.Value).ToList();

           var coordinatesExist = coordinates.Any(ed => ed.Id.ToString() == id);
           if (!Coordinates.ContainsKey(regionId) && !coordinatesExist)
            {
                   //here i want to add it but as it is list of my class i dont know how to add it  
                   Coordinates.Add(regionId, ?????);
            }
            else
            {
               return "This coordinate id already exist for this region id";
            }
        }

I have check below link but those answers are with the list of string or with an array but not with the list of class:

c# dictionary How to add multiple values for single key?

How to add values to Dictionary with a list of dictionaries inside

Sample Data :

Region Id = 100
Coordinate Id = 10,20,30

Region Id = 200
Coordinate Id = 10,20,30

1st call to Mymethod with RegionId = 100 and coordinate id =10 then I would like to have in my dictionary:Key = 100 , value = 10
2nd call to Mymethod with RegionId = 100 and coordinate id =20 then I would like to have in my dictionary:Key = 100 , value = 20
3rd call to Mymethod with RegionId = 100 and coordinate id =20 then I would like to have in my dictionary: I don't want to add this as 20 coordinate id already exist for regionId = 100

is it `Coordinates.Add(regionId, Coordinates.Where(ed => (ed.Key == regionId)).ToList());` — Developer, Jan 06 '17 at 07:33
Btw its better to name your class `Coordinate` otherwise it might confuse yourself and other people that the class itself is a list of multiple Coordinate(s). — Joel Harkes, Jan 06 '17 at 07:35
@Learning - aint this working? `Coordinates.Add(regionId, Coordinates.Where(ed => (ed.Key == regionId)).ToList())` where `Cordinates` in `Coordinates.Whe..` is list List of Class not enum — Developer, Jan 06 '17 at 07:47
Your class name `Coordinates` and dictionary variable name `Coordinates` are the same. This could cause ambiguity! — Stormenet, Jan 06 '17 at 07:51

Joel Harkes · Answer 1 · 2017-01-06T07:50:16.333

Say your class name is Coordinate and your dictionary is Coordinates

Basically:

Coordinates.Add(
  new List<Coordinate>()
  { 
    new Coordinate()
    {
      Id = coordinateId
    }
  }
); //You can remove all the whitespaace

The problem is this way (Since your code checks on if there already exists a list for the key in the dictionary) you will always only have 1 entry in your list.

So why not changes to a Dictionary<string, Coordinates>?

In json terms:

this is what you do:
{  "key" : [Coordinate] }

why not?
{  "key" : Coordinate }

Or are you trying to achieve? 
{  "key" : [Coordinate, Coordinate, Coordinate] }

Answer update

So you do, want the later: { "key" : [Coordinate, Coordinate, Coordinate] }.

You have a List inside each Dictionary entry. If a dictionary is a list of keys and values, Say in 1 dimension a List inside a dictionary is a 2 dimensional Array.

The thing is here. You need to break it up in 2 steps:

Check if the regionId key already exists in the dictionary (This means already 1 coordinate is in there(
If not: make a new list with the first coordinates.
If it does, check if the CoordinateId already exists, if not add it to the list.

Solution

public string MyMethod(string coordinateId, string regionId)
{
    if (!Coordinates.ContainsKey(regionId))
    {
        oordinates.Add(regionId, new Coordinate() {Id = regionId});
    }
    else
    {
        //Get the list of coordinates out of the dictionary for its region
        var list = Coordinates[regionId];
        if(list.Any(cor=> cor.Id == coordinateId))
        {   //Check if any of the coordinates have the same Id
            return "This coordinate id already exist for this region id";

        } else
        {  //Otherwise we add it to the list.
            lists.Add(new Coordinate() { Id = regionId})
        }

    }
    return "added";
}

Can you please post some code related to your updated answer as because i never used this kind of structure with dictionary — I Love Stackoverflow, Jan 06 '17 at 07:47
@Learning, I did, but i shouldn't have. You need to understand this basic stuff, not just copy paste it. — Joel Harkes, Jan 06 '17 at 07:53

score 1 · Answer 2 · edited May 23 '17 at 11:55

1

Use the correct data structure, a Dictionary<string, HashSet<Coordinates>>. Add the Equals and GetHashCode methods to Coordinates that compare on the id.

That way you can just add another object to the HashSet and it will only get added if it wasn't already there.

edited May 23 '17 at 11:55

Community

1
1

answered Jan 06 '17 at 07:40

zmbq

38,013
14
101
171

Can you please post some code related to what you are saying.so that by taking reference of that i can try something – I Love Stackoverflow Jan 06 '17 at 07:45
Added a couple of links. – zmbq Jan 06 '17 at 08:22

score 0 · Answer 3 · answered Jan 06 '17 at 07:32

0

Try something like this: Coordinates.Add(regionId, new List<Coordinates> { new Coordinates { Id = id, Range = ??? } });

answered Jan 06 '17 at 07:32

Oleksandr Kobylianskyi

3,281
20
33

sujith karivelil · Answer 4 · 2017-01-06T07:38:09.650

I think you are looking for this:

Coordinates.Add(regionId, new List<Coordinates>()
                        {
                          new Coordinates(){Id=1,range=10},
                          new Coordinates(){Id=2,range=110},
                          new Coordinates(){Id=3,range=1140}
                       });

If you want to initialize such dictonary means you can do like this:

Dictionary<string, List<Coordinates>> Coordinates = new Dictionary<string, List<Coordinates>>()
{ 
    {"ID1", new List<Coordinates>()
          {
            new Coordinates(){Id=1,range=10},
            new Coordinates(){Id=2,range=110},
            new Coordinates(){Id=3,range=1140}
          }
    },
    {"ID2", new List<Coordinates>()
          {
            new Coordinates(){Id=1,range=10},
            new Coordinates(){Id=2,range=110},
            new Coordinates(){Id=3,range=1140}
          }
    }
};

How to add items in dictionary in which value is list of class?

4 Answers4

Answer update

Solution