LINQ 将项目列表转换为具有冗余值的行的查找

Question

我相信标题没有多大帮助，我会在这里尝试更好地解释......希望你能帮助我。

我有这门课

public class ItemValue
{
    public string SetId {get; set;}
    public string ItemId {get; set;}
    public string Value {get; set;}
}

我有一个像这个类的对象的集合

IEnumerable<ItemValue> = new List<ItemValue>()
{
    new ItemValue
    {
        SetId = "S1",
        ItemId = "I1",
        Value = "S1I1V",
    },
    new ItemValue
    {
        SetId = "S1",
        ItemId = "I2",
        Value = "S1I2V",
    },
    new ItemValue
    {
        SetId = "S1",
        ItemId = "I3",
        Value = "S1I3V",
    },
    new ItemValue
    {
        SetId = "S2",
        ItemId = "I1",
        Value = "S2I1V",
    },
    new ItemValue
    {
        SetId = "S2",
        ItemId = "I2",
        Value = "S2I2V1",
    },
    new ItemValue
    {
        SetId = "S2",
        ItemId = "I2",
        Value = "S2I2V2",
    },
    new ItemValue
    {
        SetId = "S2",
        ItemId = "V3",
        Value = "S2I3V",
    }
};

请注意，有 2 个实例的 SetId="S2" 和 ItemId="I2" 具有不同的值

我需要的是使用 LINQ 将此集合映射到类似的东西

var expectedResult = new Lookup<string, IDictionary<string, string>>()
{
    ["S1"] = new Dictionary<string, string>() 
    {
        { ["I1"] = "S1I1V" },
        { ["I2"] = "S1I2V" },
        { ["I3"] = "S1I3V" },
    },
    ["S2"] = new Dictionary<string, string>() 
    {
        { ["I1"] = "S2I1V" },
        { ["I2"] = "S2I2V1" },
        { ["I3"] = "S2I3V" },
    },
    ["S2"] = new Dictionary<string, string>() 
    {
        { ["I1"] = "S2I1V" },
        { ["I2"] = "S2I2V2" },
        { ["I3"] = "S2I3V" },
    }
};

我自己并不擅长 LINQ，在一些不成功的 LINQ 试验和使用一堆 foreach 和 if 的丑陋解决方案之后，我现在联系您，请您对此有所了解。

如果您需要任何其他信息，请告诉我

非常感谢您！...

Answer 1

你可以用 GroupBy 和 ToDictionary/ToLookup 做类似的事情

        var dict = items.GroupBy(i => i.SetId)
            .ToDictionary(
                group => group.Key,
                group => group.ToLookup(i => i.ItemId, i => i.Value));
         dict["S2"]["I2"].ToList() // usage example

另一种选择是

var dict2 = items.ToLookup(i => (i.SetId, i.ItemId), i => i.Value);
dict2[("S2", "I2")].ToList() // usage example