Select decimal value via LINQ

I am trying to get the decimal value using LINQ in an MVC3 project.

How can I get it? it looks easy, but I can't get a unambiguous value that is not a list, which is Product.aWeekPrice.

How can I get a specific 3DayPrice? Once the 3DayPrice is received, it will be used in the case of a condition to provide different terms, as you can see in my code below:

    public decimal GetTotal(decimal price)
    {
        // Multiply product price by count of that album to get 
        // the current price for each of those product in the cart
        // sum all product price totals to get the cart total

        //In select part, I have got error, 'cannot convert type 
        //'System.Linq.IQueryable<decimal>' to 'decimal'

        decimal threeDayPrice = (from cartItems in db.Cart
                              where cartItems.cartId == ShoppingCartId
                                 select (decimal)cartItems.Product.threeDayPrice);

        decimal aWeekPrice = (from cartItems in db.Cart
                                 where cartItems.cartId == ShoppingCartId
                                 select (decimal)cartItems.Product.aWeekPrice);

        if (price == threeDayPrice)
        {
            decimal? total = (from cartItems in db.Cart
                              where cartItems.cartId == ShoppingCartId
                              select (int?)cartItems.count * cartItems.Product.threeDayPrice).Sum();
            return total ?? decimal.Zero;
        }

        else if (price == aWeekPrice)
        {
            decimal? total = (from cartItems in db.Cart
                              where cartItems.cartId == ShoppingCartId
                              select (int?)cartItems.count * cartItems.Product.aWeekPrice).Sum();
            return total ?? decimal.Zero;
        }        
    }

      

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2 answers


If your query always returns only one value, use .Single()

to get it as decimal

a set of decimal places instead.

    decimal threeDayPrice = (from cartItems in db.Cart
                          where cartItems.cartId == ShoppingCartId
                             select (decimal)cartItems.Product.threeDayPrice).Single();

    decimal aWeekPrice = (from cartItems in db.Cart
                             where cartItems.cartId == ShoppingCartId
                             select (decimal)cartItems.Product.aWeekPrice).Single();

      



If there is a chance that the query will return to more than one or null element, use First()

/ FirstOrDefault()

.

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This error message indicates that cartItems.Product.aWeekPrice is a collection and not one. Thus, you just need to select the item you want. For example:

decimal threeDayPrice = (from cartItems in db.Cart
                     where cartItems.cartId == ShoppingCartId
                     select (decimal)cartItems.Product.threeDayPrice).FirstOrDefault();

      



should remove the error message, but it will do so by selecting the first item in the "threeDayPrice" field.

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