CODEWITHSUNDEEP
c#linqlambda
user1205746
user1205746

Reputation: 3364

lambda expression with aggregation function

I am trying to learn lambda expression from Microsoft website and I am trying to apply it to a scenario I create to get deeper understanding of what the site is trying to demonstrate. I stumble in the aggregate function that associates with linq and lambda. Please advise what is the correct syntax for what I am trying to achieve. Basically, I have a class called item which has 3 properties: category, ID and weight. A category can have multiple IDs associated with it and I am thinking of getting the total weight of a category which is the sum of all individual weight of each IDs that has the category I specified. More specifically, this is the extract of my structure:

class item
    {
        public int NodeID
        { get; set; }
        public int Weight
        { get; set; }
        public int Category
        { get; set; }
    }

I have the following dictionary:

Dictionary<int,item> _itemsReceivedList=new Dictionary<int,item>();

And this is where I tried to get the total weight of a category c:

_itemsReceivedList.Select(x=>x.Value.Category==c)
.Sum( what should I put here for the predicate? )

I wanted to sum the weight of each item that has category c. Please advise. Thanks!

Upvotes: 1

Views: 1969

Answers (3)

SJuan76
SJuan76

Reputation: 24780

Write this

_itemsReceivedList.Where(x=>x.Value.Category==c).Sum(x => x.Weight);

Upvotes: 2

Sam
Sam

Reputation: 7303

int weight = _itemsReceivedList.Where(x => x.Value.Category == c)
                               .Select(s => s.Value)
                               .Sum(item => item.Weight);

I assume that c is declared somewhere else as an int

ScreenPrint

Upvotes: 3

L.B
L.B

Reputation: 116108

var sum = _itemsReceivedList
            .Where(x=>x.Value.Category==c)
            .Sum(x=>x.Value.Weight);

Upvotes: 3

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