declare variable to store linq entity for conditional statements

Question

I am trying to look up record using if I have the key then use Find if not use Where

private ApplicationDbContext db = new ApplicationDbContext();

    public bool DeactivatePrice(int priceId = 0, string sponsorUserName = "")
    {
        var prices = db.BeveragePrices;

        // if we have an id then find
        if (priceId != 0)
        {
           prices = prices.Find(priceId);
        }
        else
        {
            prices = prices.Where(b => b.UserCreated == sponsorUserName);
        }

        if (prices != null)
        {
            // do something
        }
        return true;

I get the following error for

prices = prices.Find(priceId);

Cannot convert app.Model.BeveragePrices from system.data.entity.dbset

I am copying the pattern from this answer but something must be different.

Seems you forgot to put a predicate inside the Find function call. See my answer for a fix and another option. — ilans
– ilans, Commented Oct 19, 2014 at 19:07
The Find method returns a single entity but you have prices implicitly typed as a collection. This will cause an error. — Alaa Masoud
– Alaa Masoud, Commented Oct 19, 2014 at 22:22
@Alla - I think you are right about the single entity. I'll add this to the answer. Tnx. — ilans
– ilans, Commented Oct 22, 2014 at 1:49

ilans · Accepted Answer · 2014-10-22 01:52:21Z

1

Seems you forgot to put a predicate inside the Find function call. Also you need to do ToList on the collection. The second option is a lot more efficient. The first one gets the whole collection before selection.

Another note commented by @Alla is that the find returns a single element. So I assume another declaration had been made for 'price' in the first option I state down here.

price = prices.ToList.Find(b => b.PriceId == priceId);

Or

prices = prices.Select(b => b.PriceId == priceId);

I assume the field name is PriceId.

edited Oct 22, 2014 at 1:52

answered Oct 19, 2014 at 19:00

ilans

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