计算数据集中每个日期的类别项目(使用linq的C#)

public class DataItem
{
    public DateTime Date { get; set; }
    public string Category { get; set; }
}

List<DataItem> data = new List<DataItem>
{
    new DataItem { Date = new DateTime(2022, 1, 1), Category = "A" },
    new DataItem { Date = new DateTime(2022, 1, 1), Category = "B" },
    new DataItem { Date = new DateTime(2022, 1, 2), Category = "A" },
    new DataItem { Date = new DateTime(2022, 1, 2), Category = "C" },
    new DataItem { Date = new DateTime(2022, 1, 3), Category = "B" },
};

var result = from item in data
             group item by item.Date into g
             select new
             {
                 Date = g.Key,
                 Categories = g.Select(x => x.Category).Distinct().ToList()
             };

foreach (var item in result)
{
    Console.WriteLine($"Date: {item.Date}");
    Console.WriteLine("Categories:");
    foreach (var category in item.Categories)
    {
        Console.WriteLine(category);
    }
    Console.WriteLine();
}