List ling 统计函数Distinct Sum Max Average

var langCount = (from s in GetStudents()
                           select s.Language)
                           .Distinct()
                           .Count();
        Response.Write(string.Format("<div class='result'>{0}</div>", langCount));
        #endregion

        #region 用Count()的Lambda表达式满足条件的元素个数
        Response.Write("<hr>用Count()得出查询结果的个数<br>");
        var ageCoun = (from s in GetStudents()
                          select s.Age)
                          .Count(a=>a>22);
        Response.Write(string.Format("<div class='result'>{0}</div>", ageCoun));
        #endregion

        #region 用Sum()将查询结果相加
        Response.Write("<hr>用Sum()将查询结果相加<br>");
        var ageSum = (from s in GetStudents()
                      select s.Age)
                       .Sum();
        //var ageSum = GetStudents().Sum(s=>s.Age);
        Response.Write(string.Format("<div class='result'>{0}</div>", ageSum));
        #endregion

        #region 用Min()得出查询结果的最小值
        Response.Write("<hr>用Min()得出查询结果的最小值<br>");
        var ageMin = (from s in GetStudents()
                      select s.Age)
                       .Min();
        //var ageMin = GetStudents().Min(s => s.Age);
        Response.Write(string.Format("<div class='result'>{0}</div>", ageMin));
        #endregion

        #region 用Max()得出查询结果的最大值
        Response.Write("<hr>用Max()得出查询结果的最大值<br>");
        var ageMax = (from s in GetStudents()
                      select s.Age)
                       .Max();
        //var ageMax = GetStudents().Max(s => s.Age);
        Response.Write(string.Format("<div class='result'>{0}</div>", ageMax));
        #endregion

        #region 用Average()得出查询结果的平均值
        Response.Write("<hr>用Average()得出查询结果的平均值<br>");
        var ageAverage = (from s in GetStudents()
                      select s.Age)
                      .Average();

  

var list = from it in lst
                        group it by it.产品 into g
                       select new
                       {
                           产品 = g.Key,
                           份数 = g.Sum(p=>p.份数),
                       };