如何展平嵌套对象 (LINQ)

Question

我正在旧的 Winforms 网格上做一些工作，我有两个模型，我试图展平并分配给 DataGridView。

这是我的示例模型。

public class StockItem
{
     public string StockName { get; set; }
     public int Id { get; set; }
     public List<Warehouse> Warehouses { get; set; }
}

public class Warehouse
{
     public string WarehouseName { get; set; }
     public int Id { get; set; }
}

数据的工作方式是必须首先创建一个仓库，然后将其分配给每个 StockItem。一个StockItem可能拥有所有的仓库，也可能只有一个。

我需要展平数据，以便网格显示 StockName，然后是库存项目的所有关联仓库。

例子

StockCode1      Warehouse1   Warehouse2   Warehouse3
StockCode2      Warehouse1   Warehouse2   
StockCode2      Warehouse1                Warehouse3

我试图通过 Linq 查询来执行此操作，但只能根据 StockItem\Warehouse.

获取一条记录

Answer 1

我不推荐它，但您可以使用dynamic对象来创建具有您想要的形状的对象。 这样做不是常见的 C# 模式。 这在 Python 或 Javascript 等语言中更为常见。

C# 是一种强类型语言，冒险进入动态对象的世界应该只有在绝对必要时才考虑（想想解析一个 json blob）。我强烈认为你重新评估了你需要做的事情并从不同的角度处理它。

Answer 2

这应该能满足您的需求：

var flattened = stockItems
    .Select(x => new { 
                 StockName = x.StockName, 
                 WarehouseNames = x.Warehouses
                                  .Select(y => y.WarehouseName)
                                  .ToList() })
    .ToList();

它将生成包含 StockName 和 WarehouseName 字符串列表的项目集合。 ToList 添加以枚举查询。

对于这些示例数据：

List<StockItem> stockItems = new List<StockItem>
{
    new StockItem
    {
        StockName ="A",
        Id = 1,
        Warehouses = new List<Warehouse>
        {
            new Warehouse { Id = 1, WarehouseName = "x" },
            new Warehouse { Id = 2, WarehouseName = "y" }
        }
    },
    new StockItem
    {
        StockName = "B",
        Id = 2,
        Warehouses = new List<Warehouse>
        {
            new Warehouse { Id = 3, WarehouseName = "z" },
            new Warehouse { Id = 4, WarehouseName = "w" }
        }
    }
};

我得到以下结果：

Answer 3

像这样：

var availableWarehouses = new [] { 
    new Warehouse { 
        WarehouseName = "Warehouse1",
        Id = 1
    },
    new Warehouse {
        WarehouseName = "Warehouse2",
        Id = 2
    },
    new Warehouse {
        WarehouseName = "Warehouse3",
        Id = 3
    }
};

var stocks = new [] {
    new StockItem {
        StockName = "StockCode1",
        Id = 1,
        Warehouses = new List<Warehouse> { availableWarehouses[0], availableWarehouses[1], availableWarehouses[2] }
    },
    new StockItem {
        StockName = "StockCode2",
        Id = 2,
        Warehouses = new List<Warehouse> { availableWarehouses[0], availableWarehouses[1] }
    },
    new StockItem {
        StockName = "StockCode3",
        Id = 3,
        Warehouses = new List<Warehouse> { availableWarehouses[0], availableWarehouses[2] }
    }
};

var flatten = stocks.Select(item => new {
        StockName = item.StockName,
        WarehousesNames = availableWarehouses.Select(warehouse => item.Warehouses.Contains(warehouse) ? warehouse.WarehouseName : "          ")
            .Aggregate((current, next) => current + "\t" + next)
    });

foreach(var item in flatten) {
    Console.WriteLine("{0}\t{1}", item.StockName, item.WarehousesNames);
}

Answer 4

您可以通过创建一个您可以轻松用作 gridview 源的 DataTable 来实现它。首先添加所有列，然后为每个库存添加仓库：

var warehouseNames = 
    stocks
    .SelectMany(x => x.Warehouses.Select(y => y.WarehouseName)).Distinct();

var dt = new DataTable();
dt.Columns.Add("StockCode");

foreach (var name in warehouseNames)
{
    dt.Columns.Add(name);
}

foreach (var stock in stocks)
{
    var row = dt.NewRow();
    row["StockCode"] = stock.Id;
    foreach (var warehouse in stock.Warehouses)
    {
        row[warehouse.WarehouseName] = warehouse.Id;
    }
    dt.Rows.Add(row);
}

如何展平嵌套对象 (LINQ)

How to flatten nested objects (LINQ)

c#

linq

datagridview

models