Linq:int之和 [英] Linq: Sum of int

问题描述

我得到"不能将空值分配给类型为System.Int32的成员，这是非空值类型"，当我执行空语句的Sum()时. ResultView可以正常工作，但是可以

I am getting "The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type" When executing Sum() of my empty statement. ResultView works fine, but either

var r = from v in DataContext.Visits
        join bs in DataContext.BaseContents on v.BaseContentID equals bs.Id
        where (bs.CreatedBy == userId) && (v.DateVisited.Year == workDate.Year) &&
        (v.DateVisited.Month == workDate.Month) && (v.DateVisited.Day == workDate.Day) &&
        (v.IsPreviewed == false) && (bs.ProfileProjectId != null)
        select v;

int? number = r.Sum( v => v.Counter);

两个

var r = from v in DataContext.Visits
        join bs in DataContext.BaseContents on v.BaseContentID equals bs.Id
        where (bs.CreatedBy == userId) && (v.DateVisited.Year == workDate.Year) &&
        (v.DateVisited.Month == workDate.Month) && (v.DateVisited.Day == workDate.Day) &&
        (v.IsPreviewed == false) && (bs.ProfileProjectId != null)
        select v.Counter;

int? number = r.Sum(v);

失败，具有相同的例外.

fails with same exception.

推荐答案

尝试一下(已更新):

int number = r.Sum(v => (int?)v.Counter) ?? 0;

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