How to convert integer value to datetime

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Hello Friends

I want to convert integer value 1 to convert it into datetime and then subtract it with a datetime value.
I am using this code

C#

DateTime lasttime = LastUpdateTime - Convert.ToDateTime(1);

where LastUpdateTime is DateTime type variable.
It is giving me an error

C#

Cannot implicitly convert type 'System.TimeSpan' to 'System.DateTime'.

Can any one help.

Thanks in advance

Posted 26-Jan-12 23:36pm

RashdSiddique

Updated 26-Jan-12 23:44pm

Anuja Pawar Indore

v2

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Anuja Pawar Indore 27-Jan-12 5:45am

Added pre tag

BillWoodruff 27-Jan-12 10:00am

In this type of question the intent of what you mean by "subtract it" is unclear: you leave it up to our imaginations to assume that you mean subtract one day, one hour, one ?

Please try to be very specific: tell us what the integer value #1 means in this question.

4 solutions

Solution 4

Hello RashdSiddique

there seem to be confusion on DateTime and TimeSpan.

DateTime is a specific point in time.
A TimeSpan is a duration.
The difference between two points in time (DateTime) is a duration (TimeSpan).
You cannot make a duration being a point in time.
You can add a duration to a point in time to get another specific point in time.

Use one of the several Add... methods of the DateTime class to accomplish the desired result.

Note that adding a negative amount equals to subtract that positive amount - that's why the DateTime class has no Subtract... methods.

Finally, the Convert.ToDateTime(int) seems very odd to me. As a maintainer I would dislike such code, since it is anti-intuitively and leaves a crucial question open: what unit?

Cheers

Andi

Posted 27-Jan-12 0:01am

Andreas Gieriet

Updated 27-Jan-12 4:37am

v3

Comments

BillWoodruff 27-Jan-12 9:58am

+5 Very nice comprehensive summary ! One very small suggestion: use "to get another specific point in time" in point #5.

Andreas Gieriet 27-Jan-12 10:39am

Thanks for your 5 and your suggestion for improvement!
Cheers
Andi

Solution 2

There are two problems there:
1) What do you expect to get as a date time combination from Convert.ToDateTime(1)? Because all you will get is the run time error "Invalid cast from 'Int32' to 'DateTime'."
"1" is not a date.
2) If you subtract two dates, you do not get a date - you get a time interval. "Tomorrow minus last Tuesday" will give you a number of days, not a date. Try using a TimeSpan to receive it instead.

What you are probably trying to do is work out the time interval since the last update:

C#

TimeSpan ts = DateTime.Now - LastUpdateTime;

Posted 26-Jan-12 23:45pm

OriginalGriff

Solution 3

Convert.ToDateTime(integer) is not supported.
Have a look at this[^] documentation.

Posted 26-Jan-12 23:46pm

Abhinav S

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Sanjay K. Gupta · Accepted Answer · 2012-01-26T23:39:00

Solution 1

use

C#

LastUpdateTime.AddDays(-1);

Posted 26-Jan-12 23:39pm

Sanjay K. Gupta

Updated 26-Jan-12 23:45pm

v2

Comments

Anuja Pawar Indore 27-Jan-12 5:45am

Added pre tag