C#•4mo ago

✅ Struggling to use custom comparer with a list of KeyValuePairs

I'm trying to sort a list of keyvaluepairs on the key. I've defined an IComparer using Comparer.Create, but the list after sorting is identical to before. I can't use a SortedList because that requires unique keys.

IComparer<KeyValuePair<float, int>> comp = Comparer<KeyValuePair<float, int>>.Create((a, b) => a.Key < b.Key ? 1 : 0);
List<KeyValuePair<float, int>> li = [
    new(1f, 1),
    new(1.5f, 2),
    new(2.5f, 3),
    new(0.5f, 4),
    new(0.2f, 5)
    ];
li.Sort(comp);

foreach (var kvp in li)
    Console.WriteLine(kvp.Key + ", " + kvp.Value);

IComparer<KeyValuePair<float, int>> comp = Comparer<KeyValuePair<float, int>>.Create((a, b) => a.Key < b.Key ? 1 : 0);
List<KeyValuePair<float, int>> li = [
    new(1f, 1),
    new(1.5f, 2),
    new(2.5f, 3),
    new(0.5f, 4),
    new(0.2f, 5)
    ];
li.Sort(comp);

foreach (var kvp in li)
    Console.WriteLine(kvp.Key + ", " + kvp.Value);

The output looks like

1, 1
1.5, 2
2.5, 3
0.5, 4
0.2, 5

1, 1
1.5, 2
2.5, 3
0.5, 4
0.2, 5

Whereas I'd expect it to be sorted in either ascending or descending order.

5 Replies

Angius•4mo ago

You could just OrderBy() it

MODiX•4mo ago

Angius

REPL Result: Success

List<KeyValuePair<float, int>> li = [
    new(1f, 1),
    new(1.5f, 2),
    new(2.5f, 3),
    new(0.5f, 4),
    new(0.2f, 5)
    ];
li.OrderBy(kv => kv.Key)

List<KeyValuePair<float, int>> li = [
    new(1f, 1),
    new(1.5f, 2),
    new(2.5f, 3),
    new(0.5f, 4),
    new(0.2f, 5)
    ];
li.OrderBy(kv => kv.Key)

Result: OrderedEnumerable<KeyValuePair<float, int>, float>

[
  {
    "key": 0.2,
    "value": 5
  },
  {
    "key": 0.5,
    "value": 4
  },
  {
    "key": 1,
    "value": 1
  },
  {
    "key": 1.5,
    "value": 2
  },
  {
    "key": 2.5,
    "value": 3
  }
]

[
  {
    "key": 0.2,
    "value": 5
  },
  {
    "key": 0.5,
    "value": 4
  },
  {
    "key": 1,
    "value": 1
  },
  {
    "key": 1.5,
    "value": 2
  },
  {
    "key": 2.5,
    "value": 3
  }
]

Compile: 414.906ms | Execution: 56.561ms | React with ❌ to remove this embed.

EvyrOP•4mo ago

Thank you

cap5lut•4mo ago

btw, a.Key < b.Key ? 1 : 0 is seems to be wrong. a negative value idicates that a is smaller, zero indicates that they are equal, and a positive value indicates that a is bigger.

EvyrOP•4mo ago

ah, thanks just tried both of those and they both work, thank you both

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✅ Struggling to use custom comparer with a list of KeyValuePairs