Linq 如何按时间分组？比较急，望赐教，以后再学基本功！！！

[glc20022003]

List<AFileTools.Model.ItemDataBase> lst = new List<AFileTools.Model.ItemDataBase>();
lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 20:00:00", Value = "1.1" });
lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 21:00:00", Value = "2.2" });
lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 20:00:00", Value = "3.1" });
lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 21:00:00", Value = "111.1" });

当前数据是年-月-日-小时

如何按 年-月-日 分组，都来看看。

[glc20022003]

自己搞定了

List<Model.ItemDataBase> lstData = new List<AFileTools.Model.ItemDataBase>();
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 20:00:00", Value = "1.1" });
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 21:00:00", Value = "2.2" });
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 20:00:00", Value = "3.1" });
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 21:00:00", Value = "111.1" });

            IEnumerable<IGrouping<string, string>> query =
                from Data in lstData
                group Data.Value by Data.DT.Substring(0, Data.DT.IndexOf(' '));

            foreach (IGrouping<string, string> q in query)
            {
                MessageBox.Show(q.Key);
                float avg = q.Average(s => float.Parse(s));
                MessageBox.Show(Utils.Utilitys.Round(avg, 1).ToString());
            }

[zzc_king]

按平均值分组是什么意思？

[zzc_king]

平均值从何而来。。

[q107770540]

List<Model.ItemDataBase> lstData = new List<AFileTools.Model.ItemDataBase>();
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 20:00:00", Value = "1.1" });
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 21:00:00", Value = "2.2" });
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 20:00:00", Value = "3.1" });
            lstData.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 21:00:00", Value = "111.1" });

            IEnumerable<IGrouping<string, string>> query =
                from Data in lstData
                group Data by Data.DT.Substring(0, Data.DT.IndexOf(' ')) into g
                select g.Average(s => float.Parse(s.Value));

[glc20022003]

忘记说了，是按平均值分组。

[苦苦的潜行者]

linq

            //List<AFileTools.Model.ItemDataBase> lst = new List<AFileTools.Model.ItemDataBase>();
            //lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 20:00:00", Value = "1.1" });
            //lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-1 21:00:00", Value = "2.2" });
            //lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 20:00:00", Value = "3.1" });
            //lst.Add(new AFileTools.Model.ItemDataBase() { DT = "2010-1-2 21:00:00", Value = "111.1" });

            var query = from q in db.GetList
                        group q by DateTime.Parse(q.DT).ToString("yyyy-MM-dd") into g
                        select new {DT=g.Key,Value=g.Sum(r=>float.Parse(r.NValue) ) };
            dataGridView1.DataSource=query.ToList();

类db

    public class db
    {
        string dT;
        string nValue;

        public string DT
        {
            set { dT = value; }
            get { return dT; }
        }

        public string NValue
        {
            set { nValue = value; }
            get { return nValue; }
        }

        public static List<db> GetList
        {
            get
            {
                return new List<db>() { 
                new db(){ DT = "2010-1-1 20:00:00", NValue = "1.1" },
                new db(){ DT = "2010-1-1 21:00:00", NValue = "2.2" },
                new db(){ DT = "2010-1-2 20:00:00", NValue = "3.1" },
                new db(){ DT = "2010-1-2 21:00:00", NValue = "111.1" }
            };
            }
        }
    }

[苦苦的潜行者]

[Quote=引用 1 楼 glc20022003 的回复:]

忘记说了，是按平均值分组。
[/Quote]

            var query = from q in db.GetList
                        group q by DateTime.Parse(q.DT).ToString("yyyy-MM-dd") into g
                        select new {DT=g.Key,Value=g.Average(r=>float.Parse(r.NValue) ) };
            dataGridView1.DataSource=query.ToList();