Linq SUM values error

Question

public async Task<WalletTrans> getCredits(int id) 
{
    var credit = await _context.walletTrans.ToAsyncEnumerable().Where(r => r.Id == id).Sum(s => s.quantity);
    return credit;
}

I have that code above using C#.net core that supposedly returning a summation of a filed in the table.

But I'm having this error.

"Cannot implicitly convert type 'decimal' to 'ProjectName.Models.ModelName' [ProjectName]"

Your method return type is `WalletTrans`, but you're returning `decimal` value from `Sum()` function. Adjust return type as `decimal` or assign sum value to any `decimal` property that `WalletTrans` class has. — Tetsuya Yamamoto, Aug 28 '18 at 03:52
Thanks for the answer. But I still don't get it. Can you give me sample? — Novice, Aug 28 '18 at 03:55

score 5 · Accepted Answer · answered Aug 28 '18 at 03:56

5

a sample as you asked:

public async Task<decimal> getCredits(int id)
{    
    var credit = await _context.walletTrans.ToAsyncEnumerable().Where(r => r.Id == id).Sum(s => s.quantity);   
    return credit;
}

answered Aug 28 '18 at 03:56

Access Denied

8,723
4
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how can I return this as a JSon? – Novice Aug 28 '18 at 04:02
1

do you mean a string in json format or some jobject from newtone library? Yes you can, just return not credit, but new JObject(credit) or whatever. – Access Denied Aug 28 '18 at 04:05
Take a look at the following SO thread: https://stackoverflow.com/questions/6201529/how-do-i-turn-a-c-sharp-object-into-a-json-string-in-net – Access Denied Aug 28 '18 at 04:09

score 0 · Answer 2 · answered Aug 29 '18 at 02:41

0

This will answer my question regarding on how can I return it as a JSON Object

public async Task<object> getCredits(int id){
    dynamic response = new JObject();
    try {
          decimal credit = await _context.walletTrans.ToAsyncEnumerable().Where(r => r.Id == id).Sum(s => s.quantity);
          response.Credit = credit;
          return response;
        } catch (Exception e) {
            response.Error = e;
            return response;
        }
}

Thanks for All your help :D

answered Aug 29 '18 at 02:41

Novice

183
3
14

I would avoid dynamic if you can, and just use correct types. `public async Task…` and then to fill in values, `response["Credit"] = credit` or `response["Error"] = e`. – ryzngard Aug 30 '18 at 22:33

Linq SUM values error

2 Answers2