C#用DataTable实现Group by数据统计

1、用两层循环计算，前提条件是数据已经按分组的列排好序的。

DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[] { new DataColumn("name", typeof(string)),
new DataColumn("sex", typeof(string)),
new DataColumn("score", typeof(int)) });
dt.Rows.Add(new object[] { "张三","男",1 });
dt.Rows.Add(new object[] { "张三","男",4 });
dt.Rows.Add(new object[] { "李四","男",100 });
dt.Rows.Add(new object[] { "李四","女",90 });
dt.Rows.Add(new object[] { "王五","女",77 });
DataTable dtResult = dt.Clone();
for (int i = 0; i < dt.Rows.Count; )
{
DataRow dr = dtResult.NewRow();
string name = dt.Rows[i]["name"].ToString();
string sex = dt.Rows[i]["sex"].ToString();
dr["name"] = name;
dr["sex"] = sex;
int score = 0;
//内层也是循环同一个表，当遇到不同的name时跳出内层循环
for (; i < dt.Rows.Count; )
{
if (name == dt.Rows[i]["name"].ToString()&&name == dt.Rows[i]["sex"].ToString())
{
score += Convert.ToInt32(dt.Rows[i]["score"]);
dr["score"] = score;
i++;
}
else
{
break;
}
}
dtResult.Rows.Add(dr);

}

dtResult中的数据即是最终结果。

2、 借助DataTable的Compute方法，DataTable中数据不用事先排好序。

DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[] { new DataColumn("name", typeof(string)),
new DataColumn("sex", typeof(string)),
new DataColumn("score", typeof(int)) });
dt.Rows.Add(new object[] { "张三","男",1 });
dt.Rows.Add(new object[] { "张三","男",4 });
dt.Rows.Add(new object[] { "李四","男",100 });
dt.Rows.Add(new object[] { "李四","女",90 });
dt.Rows.Add(new object[] { "王五","女",77 });
DataTable dtResult = dt.Clone();
DataTable dtName = dt.DefaultView.ToTable(true, "name","sex");
for (int i = 0; i < dtName.Rows.Count; i++)
{
DataRow[] rows = dt.Select("name='" + dtName.Rows[i][0] + "' and sex='" + dtName.Rows[i][1] + "'");
//temp用来存储筛选出来的数据
DataTable temp = dtResult.Clone();
foreach (DataRow row in rows)
{
temp.Rows.Add(row.ItemArray);
}

DataRow dr = dtResult.NewRow();
dr[0] = dtName.Rows[i][0].ToString();
dr[1] = temp.Compute("sum(score)", "");
dtResult.Rows.Add(dr);

}

3、使用linq to DataTable group by实现

var query = from t in dt.AsEnumerable()
group t by new { t1 = t.Field<string>("name"), t2 = t.Field<string>("sex") } into m
select new
{
name = m.Key.t1,
sex = m.Key.t2,
score = m.Sum(n => n.Field<decimal>("score"))
};
if (query.ToList().Count > 0)
{
query.ToList().ForEach(q =>
{
Console.WriteLine(q.name + "," + q.sex + "," + q.score);
});
}