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[英]Entity Framework 4.0/ How to concatenate string from date and time
[英]Entity framework “Select date time from string”
我需要从表中选择日期间隔的记录。
但是在此模式中,可供选择的日期保留为nvarchar
20160511_155015 (yyyymmdd_hhmmss)
我不能使用ToList()
将其设置为DateTime.ParseExact(entry.StartDate, "yyyyMMdd_HHmmss", CultureInfo.InvariantCulture)
该表保留了数百万条记录。 所以我需要做这样的事情:
var preQuery = context.Table
.AsNoTracking()
.Select(x => new
{
StartDate = ConvertFrom()),
Mode = x.Mode,
SessionStart = x.AStart,
SessionEnd = x.AEnd,
x.SensorNumber
})
.Where(x => x.StartDate != null
&& x.StartDate >= startDate
&& x.StartDate <= endDate)
.ToList();
是否可以将字符串表示形式转换为Datetime,然后继续执行Where子句?
您可以尝试:StartDate.StartsWith(“ 20160511”)左右。.或Convert.ToInt32(StartDate.Substring(0,8))> 20160511
顺便说一句,我认为您可能想要运行一个脚本,只要它需要,并创建一个新列,该列将基于该列生成DateTime
请尝试使用此
DateTime.ParseExact(dateTime ,format,CultureInfo.InvariantCulture);
var preQuery = context.Table.AsNoTracking().Select(x => new
{
StartDate = ConvertFrom(),
Mode = x.Mode,
SessionStart = DateTime.ParseExact(x.AStart,"yyyyMMdd_HHmmss", CultureInfo.InvariantCulture),
SessionEnd = DateTime.ParseExact(x.AEnd,"yyyyMMdd_HHmmss", CultureInfo.InvariantCulture),
x.SensorNumber
})
.Where(x => x.StartDate != null && x.StartDate >= startDate && x.StartDate <= endDate)
.ToList();
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