C# 如何仅将 Linq 中的 DateTime 类型中的 Date 与 SQL with Entity Framework 进行比较？
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How to compare only Date without Time in DateTime types in Linq to SQL with Entity Framework?
提问by Sruly
Is there a way to compare two DateTimevariables in Linq2Sqlbut to disregard the Time part.
有没有办法比较两个DateTime变量，Linq2Sql但忽略时间部分。
The app stores items in the DB and adds a published date. I want to keep the exact time but still be able to pull by the date itself.
该应用程序将项目存储在数据库中并添加发布日期。我想保留确切的时间，但仍然能够按日期本身提取。
I want to compare 12/3/89 12:43:34and 12/3/89 11:22:12and have it disregard the actual time of day so both of these are considered the same.
我想比较12/3/89 12:43:34并12/3/89 11:22:12让它忽略一天中的实际时间，所以这两个被认为是相同的。
I guess I can set all the times of day to 00:00:00before I compare but I actually do want to know the time of day I just also want to be able to compare by date only.
我想我可以00:00:00在比较之前设置一天中的所有时间，但实际上我确实想知道一天中的时间，我也希望能够仅按日期进行比较。
I found some code that has the same issue and they compare the year, month and day separately. Is there a better way to do this?
我发现了一些具有相同问题的代码，它们分别比较了年、月和日。有一个更好的方法吗？
采纳答案by Quintin Robinson
try using the Dateproperty on the DateTimeObject...
尝试使用对象Date上的属性DateTime...
if(dtOne.Date == dtTwo.Date)
....
回答by Reed Copsey
For a true comparison, you can use:
要进行真正的比较，您可以使用：
dateTime1.Date.CompareTo(dateTime2.Date);
回答by Adam Robinson
In your join or where clause, use the Dateproperty of the column. Behind the scenes, this executes a CONVERT(DATE, <expression>)operation. This should allow you to compare dates without the time.
在您的 join 或 where 子句中，使用Date列的属性。在幕后，这会执行一个CONVERT(DATE, <expression>)操作。这应该允许您比较没有时间的日期。
回答by Hetuk Upadhyay
int o1 = date1.IndexOf("-");
int o2 = date1.IndexOf("-",o1 + 1);
string str11 = date1.Substring(0,o1);
string str12 = date1.Substring(o1 + 1, o2 - o1 - 1);
string str13 = date1.Substring(o2 + 1);
int o21 = date2.IndexOf("-");
int o22 = date2.IndexOf("-", o1 + 1);
string str21 = date2.Substring(0, o1);
string str22 = date2.Substring(o1 + 1, o2 - o1 - 1);
string str23 = date2.Substring(o2 + 1);
if (Convert.ToInt32(str11) > Convert.ToInt32(str21))
{
}
else if (Convert.ToInt32(str12) > Convert.ToInt32(str22))
{
}
else if (Convert.ToInt32(str12) == Convert.ToInt32(str22) && Convert.ToInt32(str13) > Convert.ToInt32(str23))
{
}
回答by Devarajan.T
DateTime dt1 = DateTime.Now.Date;
DateTime dt2 = Convert.ToDateTime(TextBox4.Text.Trim()).Date;
if (dt1 >= dt2)
{
MessageBox.Show("Valid Date");
}
else
{
MessageBox.Show("Invalid Date... Please Give Correct Date....");
}
回答by dgsjr
DateTime econvertedDate = Convert.ToDateTime(end_date);
DateTime sconvertedDate = Convert.ToDateTime(start_date);
TimeSpan age = econvertedDate.Subtract(sconvertedDate);
Int32 diff = Convert.ToInt32(age.TotalDays);
The diff value represents the number of days for the age. If the value is negative the start date falls after the end date. This is a good check.
diff 值表示年龄的天数。如果值为负，则开始日期晚于结束日期。这是一个很好的检查。
回答by Alejandro del Río
This is how I do this in order to work with LINQ.
这就是我为了与 LINQ 一起工作而这样做的方式。
DateTime date_time_to_compare = DateTime.Now;
//Compare only date parts
context.YourObject.FirstOrDefault(r =>
EntityFunctions.TruncateTime(r.date) == EntityFunctions.TruncateTime(date_to_compare));
If you only use dtOne.Date == dtTwo.Dateit wont work with LINQ (Error: The specified type member 'Date' is not supported in LINQ to Entities)
如果您只使用dtOne.Date == dtTwo.Date它，则它不适用于 LINQ（错误：LINQ to Entities 中不支持指定的类型成员“日期”）
回答by Mohan Sharma
DateTime dt1=DateTime.ParseExact(date1,"dd-MM-yyyy",null);
DateTime dt2=DateTime.ParseExact(date2,"dd-MM-yyyy",null);
int cmp=dt1.CompareTo(dt2);
if(cmp>0) {
// date1 is greater means date1 is comes after date2
} else if(cmp<0) {
// date2 is greater means date1 is comes after date1
} else {
// date1 is same as date2
}
回答by Code Geek
DateTime? NextChoiceDate = new DateTime();
DateTIme? NextSwitchDate = new DateTime();
if(NextChoiceDate.Value.Date == NextSwitchDate.Value.Date)
{
Console.WriteLine("Equal");
}
You can use this if you are using nullable DateFields.
如果您使用可为空的 DateFields，则可以使用它。
回答by Korayem
If you're using Entity Framework < v6.0, then use EntityFunctions.TruncateTimeIf you're using Entity Framework >= v6.0, then use DbFunctions.TruncateTime
如果您使用的是实体框架 < v6.0，则使用EntityFunctions.TruncateTime如果您使用的是实体框架 >= v6.0，则使用DbFunctions.TruncateTime
Use either (based on your EF version) around any DateTimeclass property you want to use inside your Linq query
围绕DateTime要在 Linq 查询中使用的任何类属性使用（基于您的 EF 版本）
Example
例子
var list = db.Cars.Where(c=> DbFunctions.TruncateTime(c.CreatedDate)
>= DbFunctions.TruncateTime(DateTime.UtcNow));
