Linq查询 - 将查询结果转换为datetime [英] Linq query - convert query result to datetime

问题描述

在我的第一个查询（stringdQuery）中，我试图传递一个字符串日期。

In my first query (stringdQuery) I am trying to pass a string date.

var stringQuery = (from p in db.Database_CRE_Events
                   select new Loan()
                   {
                       cDate = p.LastUpdated

                   }).FirstOrDefault();

然后我想将第一个查询的字符串日期转换为datetime。这是因为，我将在我的第二个查询（dateQuery）中使用此日期，where子句只接受datetime类型字段。

Then I would like to convert string date from the first query into datetime. This is because, I would use this date in my second query (dateQuery) in where clause which only accepts datetime type field.

if (stringdQuery != null && stringdQuery.cDate.HasValue)
         {
             dtt = Convert.ToDateTime(stringdQuery);

         }

var dateQuery = (from p in db.Database_CRE_Events.Where(c => c.LastUpdated == dtt)
                select new Loan()
                {
                    latest = p.Date

                }).FirstOrDefault();

当我执行此功能时，在客户端，我被抛出错误 - 无法将STW_V1.Controllers.Loan类型的对象强制转换为System.IConvertible



以下行出错：

When I execute this function and on the client-side, I get thrown error – Unable to cast object of type 'STW_V1.Controllers.Loan' to type 'System.IConvertible

Error on the following line:

dtt = Convert.ToDateTime(stringQuery); 

我在代码中遗漏了什么？



提前道歉，如果上述说明不明确，请随时提出进一步的问题。



谢谢

Am I missing something in the code?

Apology in advance, if the above explanation is not clear but please feel free to ask any further questions.

Thank you

推荐答案

有两个问题：



1： stringdQuery 的类型为贷款。所以你试图将Loan-object转换为DateTime。但首先不需要转换 - 只需通过其.Value属性访问stringdQuery.cDate的DateTime值：

There are two problems:

1: stringdQuery is of type Loan. So you're trying to convert a Loan-object to DateTime. But conversion isn't neccessary in the first place - just access the DateTime-value of stringdQuery.cDate by its .Value-property:

dtt = stringdQuery.cDate.Value;

2：我不知道你的意图是什么，但你的两个问题对我来说没什么意义：您正在查询第一个 Database_CRE_Event ，获取其 LastUpdated -date，然后查询其LastUpdated-的第一个Database_CRE_Event-日期等于前者。这与第一个查询相同。你也可以先选择 Date -property。

2: I don't know what your intention is here but your two queries don't make much sense to me: You're querying for the first Database_CRE_Event, get its LastUpdated-date and then query for the first Database_CRE_Event whose LastUpdated-date is equal to the former. Which will be the same as from the first query. You could as well select the Date-property in the first place.

这篇关于Linq查询 - 将查询结果转换为datetime的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！