C# - LINQ -按日期范围分组收集

// 假设有一个包含日期和值的数据集合
List<DataItem> data = new List<DataItem>
{
    new DataItem { Date = new DateTime(2022, 1, 1), Value = 10 },
    new DataItem { Date = new DateTime(2022, 1, 2), Value = 20 },
    new DataItem { Date = new DateTime(2022, 1, 3), Value = 30 },
    new DataItem { Date = new DateTime(2022, 2, 1), Value = 40 },
    new DataItem { Date = new DateTime(2022, 2, 2), Value = 50 },
    new DataItem { Date = new DateTime(2022, 2, 3), Value = 60 }
};

// 使用LINQ按月份进行分组收集
var result = from item in data
             group item by new { item.Date.Year, item.Date.Month } into g
             select new
             {
                 Month = g.Key,
                 Sum = g.Sum(item => item.Value),
                 Count = g.Count()
             };

// 输出结果
foreach (var item in result)
{
    Console.WriteLine($"Month: {item.Month.Year}-{item.Month.Month}, Sum: {item.Sum}, Count: {item.Count}");
}