如何查詢/轉換資料為所需格式

我想知道是否有人可以幫助我將以下資料（從資料庫中）轉換為 List。：

進入下面的物件。

public class View
{
  public List<LorryLoading> Report
}

public class LorryLoading
{
  public int LorryId
  public List<Product> Product
}

public class Product
{
  public int ProductId
  public decimal Qty0 sum(Quantity) WHERE QtyType = 0
  public decimal Qty2 sum(Quantity) WHERE QtyType = 2
  public decimal Qty3 sum(Quantity) WHERE QtyType = 3
  public List<string> Comments
}

是否可以使用單個投影？在分配串列時遇到問題。

另外，我可以在其中學習此類轉換的任何鏈接嗎？到目前為止，我發現的例子相當簡單或解釋得很差。

uj5u.com熱心網友回復：

您要問的是轉換，因此沒有簡單的投影。你可能可以用一個超級復雜的陳述句來做到這一點，這會讓你的同事在必須維護時換作業:) 我的建議是不要試圖給校園留下深刻印象，而是專注于干凈的代碼：

var lorryLoadingReport = new List<ReportData>();
//Presume you already have data into a transport object and know how to read that, as it wasn't your question

var view = new View
{
    Report = new List<LorryLoading>()
};
var listOf = new List<Product>();
        
//Lets not over complicate our mind, just keep it simple, let's get the products and the lorries
var productsList = lorryLoadingReport.Select(x => x.ProductId).ToList();
var lorriesList = lorryLoadingReport.Select(x => x.LorryId).ToList();
foreach (var lorry in lorriesList)
{
    //We'll need an entry even if the list will be empty
    var lorryLoading = new LorryLoading
    {
        LorryId = lorry,
        Product = new List<Product>()
    };

    //Get the respective subset
    var lorryLoadingReportPerLorry = lorryLoadingReport.Where(l => l.LorryId == lorry);
    if (lorryLoadingReportPerLorry.Any())
    {
        foreach (var productId in productsList)
        {
            //And add a product with all 4 sums iteratively
            var p = new Product
            {
                ProductId = productId,
                Comments = new List<string>()
            };
            var commentsList = lorryLoadingReport.Where(x => x.ProductId == productId && x.IsComment == "t").Select(s => s.Comment).ToList();
            if(commentsList.Any())
                p.Comments.AddRange(commentsList);
            p.Qty0 = lorryLoadingReport.Where(x => x.Qty == 0).Sum(y => y.Qty);
            p.Qty2 = lorryLoadingReport.Where(x => x.Qty == 2).Sum(y => y.Qty);
            p.Qty3 = lorryLoadingReport.Where(x => x.Qty == 3).Sum(y => y.Qty);

            lorryLoading.Product.Add(p);
        }
    }    
    view.Report.Add(lorryLoading);
}

uj5u.com熱心網友回復：

您可以使用 LinqAggregate進行自定義聚合。這稍微復雜一些，因為您在這里進行了雙重聚合。

請注意，這可能僅適用于 Linq-to-Objects。

var report = data
    .GroupBy(row => row.Lorryid)
    .Select(l => new LorryLoading {
        LorryId = l.Key,
        Product = l
            .GroupBy(row => row.productid)
            .Select(p => p.Aggregate(
                new Product {ProductId = p.Key},  // this is the starting object
                (prod, row) => {                  // this aggregates it up
                    if(comment != null)
                        prod.Comments.Add(row.comment);
                    if(QtyType == 0)
                        prod.Qty0  = row.Quantity;
                    else if(QtyType == 2)
                        prod.Qty2  = row.Quantity;
                    else if(QtyType == 3)
                        prod.Qty3  = row.Quantity;
                })
            .ToList()
     }).ToList();

var view = new View {Report = report};

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