c# - 使用 linq 按日期查询分组填充数据表中的缺失日期

Question

我正在尝试在数据表中填写缺失的日期以进行报告。例如：

数据表集合：

2010-01-01 : 5
2010-01-02 : 4
2010-01-03 : 2
2010-01-05 : 6

但我想要这样的结果：

2010-01-01 : 5
2010-01-02 : 4
2010-01-03 : 2
2010-01-04 : 0
2010-01-05 : 6

var total = from row in dt2.AsEnumerable() 
            where row.Field<UInt32>("Super Category") == j 
            group row by row.Field<string>("Activation Date") into sales 
            orderby sales.Key 
            select new 
                   { 
                       Name = sales.Key, 
                       CountOfClients = sales.Count() 
                   };

我怎样才能做到这一点？

Answer 1

这有效：

        DataTable dt = new DataTable();
        dt.Columns.Add(new DataColumn("dt", typeof(DateTime)));
        dt.Columns.Add(new DataColumn("num", typeof(int)));
        dt.Rows.Add(new DateTime(2010, 1, 1), 5);
        dt.Rows.Add(new DateTime(2010, 1, 2), 4);
        dt.Rows.Add(new DateTime(2010, 1, 3), 2);
        dt.Rows.Add(new DateTime(2010, 1, 5), 6);
        dt.Rows.Add(new DateTime(2010, 1, 8), 6);
        dt.Rows.Add(new DateTime(2010, 1, 9), 6);
        dt.Rows.Add(new DateTime(2010, 1, 12), 6);

        DateTime minDT = dt.Rows.Cast<DataRow>().Min(row => (DateTime)row["dt"]);
        DateTime maxDT = dt.Rows.Cast<DataRow>().Max(row => (DateTime)row["dt"]);

        // Create all the dates that should be in table
        List<DateTime> dts = new List<DateTime>();
        DateTime DT = minDT;
        while (DT <= maxDT)
        {
            dts.Add(DT);
            DT = DT.AddDays(1);
        }

        // Find the dates that should be in table but aren't
        var DTsNotInTable = dts.Except(dt.Rows.Cast<DataRow>().Select(row => (DateTime)row["dt"]));

        foreach (DateTime dateTime in DTsNotInTable)
            dt.Rows.Add(dateTime, 0);

        // Order the results collection
        var ordered = dt.Rows.Cast<DataRow>().OrderBy(row => (DateTime)row["dt"]);

        // Create a DataTable object
        DataTable dt2 = ordered.CopyToDataTable();

dt2表将包含按列DateTime排序的没有间隙的结果。DateTime

Answer 2

尝试这样的事情。

DateTime startDate = collection.first().date;
DateTime endDate = collection.last().date;

While(startDate < endDate)
{
    // compare if collection date is valid
    startDate.AddDays(1);
}