Question

我有一个模型，我正在尝试计算加权平均值：

  public class ObScore
  {
    public int ObScoreId { get; set; }
    public int AnalystId { get; set; }
    public DateTime Date { get; set; }
    public int PossScore { get; set; }
    public int Weight { get; set; }
  }

我可以使用以下代码执行此操作：

    //
    // GET: /Test/

    public ActionResult Test()
    {
        var scores = db.ObScores.ToList();

        double weightedValueSum = scores.Sum(x=>x.PossScore * x.Weight);
        double weightSum = scores.Sum(x => x.Weight);

        if (weightSum != 0)
        {
            ViewBag.wa2 = weightedValueSum / weightSum;
        }
        return View();
    }

但是，我希望能够添加GroupBy子句，因此我可以按Date / AnalystId等进行分组。

是否可以组合两个LINQ语句，以便我可以这样做，同时如果weightSum = 0，仍然可以避免DIV / 0？

谢谢，Mark

Answer 1

使用如下表达式：

div = weightSum != 0 ? weightedValueSum / weightSum : -1

最后它应该是这样的：

var res = scores.GroupBy(p => p.Date.Year)
                .Select(p => new { 
                    Year = p.Key,
                    weightedValueSum = p.Sum(x => x.PossScore * x.Weight), 
                    weightSum = p.Sum(x => x.Weight) 
                })
                .Select(p => new {
                    Year = p.Year,
                    wa2 = p.weightSum != 0 ? p.weightedValueSum / p.weightSum : -1
                })
                .ToArray();

在完整的LINQ语法

中，这应该或多或少等同于此

var res2 = (from p in scores
            group p by p.Date.Year into p
            let Year = p.Key
            let weightedValueSum = p.Sum(x => x.PossScore * x.Weight)
            let weightSum = p.Sum(x => x.Weight)
            select new {
                Year = Year,
                wa2 = weightSum != 0 ? weightedValueSum / weightSum : -1
            }).ToArray();

Linq Group同时避免Div / 0

1 个答案: