Linq to SQL处理可空值

Question

我有一个旧版SQL脚本，通过比较日期范围为low_amt和high_amt的天数，将prob_contact表与其他表连接在一起。使用SQL可以正常工作。

JOIN prob_contact p ON (s.end_date - s.start_date) BETWEEN p.low_amt AND p.high_amt

我想将SQL脚本转换为Linq，但是在可为空的TimeSpan上遇到问题？请让我知道是否有解决此问题的方法。

let d = s.End_date - s.Start_date

Original T-SQL Command (datasource Oracle 12c by Joan Casteel)

SELECT (c.last + ', ' + c.first) AS name, s.start_date, s.end_date, p.con_freq
  FROM dbo.criminals c INNER JOIN dbo.sentences s ON c.criminal_id = s.criminal_id
       INNER JOIN dbo.prob_officers o ON o.prob_id = s.prob_id
       JOIN prob_contact p ON (s.end_date - s.start_date) BETWEEN p.low_amt AND p.high_amt
  ORDER BY name, s.start_date;

Linqpad script

var result = from c in Criminals 
                join s in Sentences on c.Criminal_id equals s.Criminal_id
                let d = s.End_date - s.Start_date
                from p in Prob_contacts where d < p.Low_amt
                orderby c.Last
                select new  {
                    name = c.Last + ", " + c.First,
                    startDate = s.Start_date,
                    freq = p.Con_freq,
                    d
                };

Answer 1

希望我能正确理解您的要求。引发错误（在OP中随附的屏幕快照中，在发布答案后对其进行编辑之前，已抛出该错误），因为您正在将TimeSpan（d为查询中的TimeSpan）与Int32进行比较。根据您给出的描述，您想比较Low_amt的天数

您需要的是TimeSpan.TotalDays

from p in Prob_contacts where d.Value.TotalDays < p.Low_amt //(.Value) Since it is nullable as suggested in the error