Loop through a list and combine totals where an identifier is the same

问题

I cuurently have a list of objetcs Cars The variables within are:

Make

Model

Service Cost

Lets say I have the list filled up with:

Ferrari, F50, 300

Porsche, 911, 700

Toyota, Camary, 300

Porsche, 911, 400

BMW, Z4, 1200

Porsche, 911, 900

Porsche, 356A, 700

As you can see, my list contains three records where the Porsche 911 has service costs.

How would I loop through my list, find the duplicate 911's and combine them to form one single record? So that I end up with:

Ferrari, F50, 300

Porsche, 911, 2000

Toyota, Camary, 300

BMW, Z4, 1200

Porsche, 356A, 700

What I've done so far is not going to work, as my records would propbably end up in the wrong areas:

    List<Car> CombinedCarRecords = new List<Car>(CarDetailRecords); //Original list here being used
    List<Car> NormalList = new List<Car>();
    List<Car> NewList = new List<Car>();//Making new lists to keep the records in
    Car normalRecord = new Car();
    Car combinedRecord = new Car();//new objects to keep the values in and add the others
    string oldVal = "";
    string newVal = "";//used to find the same cars
    foreach (var item in CombinedCarRecords )
    {
        normalRecord = new ClaimDetailRecord();
        combinedRecord = new ClaimDetailRecord();
        oldVal = newVal;
        newVal = item.Model;
        if (oldVal == newVal)
        {
            combinedRecord = item;
            CombinedCarRecords.Add(combinedRecord);
        }
        else
        {
            normalRecord = item;
            NormalList.Add(normalRecord);
        }
    }//I think the way I try to find the records here is not working, as the old and new values will always be different, if maybe not for some records where they are right after each other. But there is still that initial one

    decimal totalP = 0;

    if (CombinedTariffsRecords.Count > 0)
    {
        foreach (var item in CombinedTariffsRecords)
        {
        }
    }
    else
        NewList = NormalList;
    //This is where I'm supposed to add up the totals, but I think my code before will render this code useless

So in all,I have tried, but I cannot come up with a better way to store the values and combine my records.

回答1:

The easiest way is to use LINQ's Enumerable.GroupBy and Sum:

var newCarList = NormalList
   .GroupBy(c => new {  c.Make, c.Model })
   .Select(carGroup => new Car{ 
       Make = carGroup.Key.Make, 
       Model = carGroup.Key.Model,
       ServiceCost = carGroup.Sum(c => c.ServiceCost)
    })
   .ToList();

回答2:

void Main()
{
    var cars = new List<Car> 
    { 
        new Car { Make = "Ferrari", Model = "F50", ServiceCost = 1000 },
        new Car { Make = "Ferrari", Model = "F50", ServiceCost = 2000 },
        new Car { Make = "Porsche", Model = "911", ServiceCost = 2000 }
    };
    var grouped = cars.GroupBy(car => car.Make + car.Model).Select(g => new { g.Key, Costs = g.Sum(e => e.ServiceCost), Element = g.First() });
    foreach (var g in grouped)
    {
        Console.WriteLine("{0} {1}: {2}", g.Element.Make, g.Element.Model, g.Costs);
    }
}

class Car
{
    public string Model { get; set; }

    public string Make { get; set; }

    public decimal ServiceCost { get; set; }    
}

来源：https://stackoverflow.com/questions/41097071/loop-through-a-list-and-combine-totals-where-an-identifier-is-the-same

标签

loops

foreach