LINQ：区分和合并值

Question

假设我有以下列表

        var list = new List<CustomClass>
        {
            new CustomClass {Group = "Car", Color = "White"},
            new CustomClass {Group = "Motocycle", Color = "Blue"},
            new CustomClass {Group = "Car", Color = "Black"},
        };

如何将此列表设置为不同的Group并将Color与逗号合并，以便我的列表为：

Group            Color
------------------------------------
"Car"           "White, Black"
"Motocycle"     "Blue"

Answer 1

假设您想要一个新的CustomClass List，请使用string.join和groupby

var list = new List<CustomClass>
{
    new CustomClass {Group = "Car", Color = "White"},
    new CustomClass {Group = "Motocycle", Color = "Blue"},
    new CustomClass {Group = "Car", Color = "Black"},
};

var results = list.GroupBy(c => c.Group).Select(g => new CustomClass()
    {
        Group = g.Key,
        Color = String.Join(", ", g.Select(c=>c.Color))
    }).ToList();

Answer 2

我不确定您希望将结果存储在哪个结构中。

这将为您提供包含所需结果的字典。

var colors =
    list.GroupBy(x => x.Group)
        .ToDictionary(x => x.Key, x => string.Join(", ", x.Select(y => y.Color)));

Answer 3

试试这个：

    var query =
        from x in list
        group x.Color by x.Group into gcs
        select new
        {
            Group = gcs.Key,
            Colors = String.Join(", ", gcs),
        };

我得到了这个结果：