Question

忘了最了解linq，现在需要回顾一下它是什么。它是如何工作的。现在我需要帮助。请帮帮我。非常感谢你。

var everyMonthMoneySum = new EveryMonthMoneySum()
{
    M_01 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 1)
            select o.Signmoney).Sum(),
    M_02 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 2)
            select o.Signmoney).Sum(),
    M_03 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 3)
            select o.Signmoney).Sum(),
    M_04 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 4)
            select o.Signmoney).Sum(),
    M_05 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 5)
            select o.Signmoney).Sum()+5,
    ...........................
    M_11 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 11)
            select o.Signmoney).Sum(),
    M_12 = (from o in temp.Where(o => o.IsSign == (short) OrderStateEnum.Success && o.SignMonth == 12)
            select o.Signmoney).Sum()

};

Answer 1

听起来像你可以用字典做的那样：

var results = temp.Where(o => o.IsSign == (short) OrderStateEnum.Success)
                  .GroupBy(o => o.SignMonth)
                  .ToDictionary(g => g.Key, g => g.Sum(o => o.SignMoney));

请注意，赢了填充字典，其中包含＆＃34;缺少＆＃34;个月。

这将为您提供一个集合，而不是12个不同的变量。就个人而言，我发现这通常是一种更好的方法，但我们真的不知道你试图用这12个值做什么...

如果你想确保填充字典，我会个人之后再做一次额外的循环：

for (int i = 1; i <= 12; i++)
{
    if (!results.ContainsKey(i))
    {
        results[i] = 0m;
    }
}

它不是＆＃34;聪明＆＃34;，但它有效。或者，您可以从字典中填充数组：

var array = new decimal[13]; // 0 to 12 *inclusive*
foreach (var entry in array)
{
    array[entry.Key] = entry.Value;
}

在LINQ语句中还有其他方法可以完成所有操作，但我不知道他们如何使用您正在使用的任何LINQ提供程序（我们都不知道）而且他们更复杂。

Answer 2

使用GroupBy和Where过滤掉值，然后按SignMonth分组，如：

var query = temp.Where(o => o.IsSign == (short) OrderStateEnum.Success)
    .GroupBy(r => r.SignMonth)
    .Select(grp => new
    {
        Month = grp.Key,
        Sum = grp.Sum(t => t.Signmoney)
    });

Linq：如何使用一行代码轻松实现这一目标？

2 个答案: