C#•5mo ago

Aggregate data grouped by a key

I'm looking to aggregate these data:

// from this
[
  new { id = 1, qty = 3 },
  new { id = 2, qty = 5 },
  new { id = 1, qty = 10 },
]

// to this
[
  new { id = 1, qty = 13 },
  new { id = 2, qty = 5 },
]

// from this
[
  new { id = 1, qty = 3 },
  new { id = 2, qty = 5 },
  new { id = 1, qty = 10 },
]

// to this
[
  new { id = 1, qty = 13 },
  new { id = 2, qty = 5 },
]

my current approach iterates over the list into a dictionary and check for duplicate keys. i have a feeling it can be done in a cleaner way with System.Linq stuff

4 Replies

Angius•5mo ago

.GroupBy() with .Select() and .Sum() could work

MODiX•5mo ago

Angius

REPL Result: Success

record Item(int Id, int Qty);

Item[] items = {
    new(1, 3),
    new(2, 5),
    new(1, 10),
};

var newItems = items
    .GroupBy(i => i.Id)
    .Select(g => new Item(g.Key, g.Sum(i => i.Qty)));

newItems

record Item(int Id, int Qty);

Item[] items = {
    new(1, 3),
    new(2, 5),
    new(1, 10),
};

var newItems = items
    .GroupBy(i => i.Id)
    .Select(g => new Item(g.Key, g.Sum(i => i.Qty)));

newItems

Result: List<Item>

[
  {
    "id": 1,
    "qty": 13
  },
  {
    "id": 2,
    "qty": 5
  }
]

[
  {
    "id": 1,
    "qty": 13
  },
  {
    "id": 2,
    "qty": 5
  }
]

Compile: 588.693ms | Execution: 99.162ms | React with ❌ to remove this embed.

Angius•5mo ago

'Ere

cheeze2000OP•5mo ago

oh thanks

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Aggregate data grouped by a key