SQL＆C＃ - 我有一个查询给了我想要的所有细节，但我不知道如何获得总价

Question

下面是我的代码和我从中得到的输出。 我得到正确的输出，但我需要计算总价格，我不知道如何去做。

任何帮助深表感谢

// Search Database
if (query.Any()) 
{
    int carID = query.FirstOrDefault().Id;
    string carRegg = query.FirstOrDefault().regNo;
    string carMake = query.FirstOrDefault().Make;
    string carModel = query.FirstOrDefault().Model;
    int hourS = query1.FirstOrDefault().Hours;
    DateTime dateS = query1.FirstOrDefault().Date;

    var test = (from a in dbC.Cars
                where a.Id == carID
                join b in dbC.Services on a.Id equals b.CarId
                join c in dbC.PartsUseds on b.ServiceWrkNo equals c.ServiceServiceWrkNo
                join d in dbC.Parts on c.PartsPartNo equals d.PartNo
                where a.Id == carID && b.Date == ((from b1 in dbC.Services where b1.CarId == b.CarId select b1.Date).Max())
                select new
                       {
                           serviceNum = b.ServiceWrkNo,
                           date = b.Date,
                           PartNo = c.PartsUsedNo,
                           replacedParts = d.PartName,
                           priceP = d.Price,
                           hourS = b.Hours
                       }).ToList();

    Console.WriteLine();
    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - ");
    Console.WriteLine("CAR SERVICE DETAILS: \t\t " + carMake + " " + carModel);
    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - " + "\n");

    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - ");
    Console.WriteLine("LAST SERVICE TOOK PLACE ON:\t " + dateS.ToShortDateString());
    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - " + "\n");

    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - ");
    Console.WriteLine("HOURS SPENT ON THE SERVICE:\t " + hourS);
    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - " + "\n");

    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - ");
    Console.WriteLine("PARTS USED:   \t\t\tPRICE      PART");
    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - " + "\n");

    foreach (var item in test)
    {
        Console.WriteLine("\t\t\t        " + item.priceP + "\t   " + item.replacedParts);
    }

    Console.WriteLine("- - - - - - - - - - - - - - - - - - - - - - - - - - - - " + "\n");
}

在此输入图像描述

Answer 1

由于test是包含您要求总和的所有元素的List ，因此您可以使用Linq来计算总数，如下所示：

var total = test.Sum(x => x.priceP);

除此之外，我将为这些调用引入一个临时变量：

int carID = query.FirstOrDefault().Id;
string carRegg = query.FirstOrDefault().regNo;
string carMake = query.FirstOrDefault().Make;
string carModel = query.FirstOrDefault().Model;
int hourS = query1.FirstOrDefault().Hours;
DateTime dateS = query1.FirstOrDefault().Date;

像这样：

var result = query.FirstOrDefault();
int carID = result.Id;
string carRegg = result.regNo;
string carMake = result.Make;
string carModel = result.Model;
int hourS = result.Hours;
DateTime dateS = result.Date;

这应该可以提高性能，因为您可以防止之前可能发生的多个数据库调用