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Conversion in SqlDbType.DateTime2 is approximative

I'm working in C# and I need to add a value in a row of my SQL database. The value needs to be of type DateTime2. So I have to do things that way :
query.Parameters.Add("Expiration", SqlDbType.DateTime2).Value = expiration; because expiration is of type DateTime. When it's done, I can execute my query without any problem.
But the value inserted in the database is not strictly the same than the value expiration. expiration equals to {09:48:47.6721345} and the value in the database is {09:48:47.6720000}. So there's fractional seconds missing, because of the conversion.
How can I manage that problem ?

as you specified the field in the database is datetime and the value that you are sending is datetime2 so the insertion query will send a datetime2 value but the result will be saved as datetime
according to the docs datetime has .123 for precision where datetime2 has .1234567

You mentioned that
expiration is of type DateTime
If that's the case, your truncation happened when you create the expiration object, who then pass that truncated value to the database.
By the way, when you mention
expiration equals to {09:48:47.6721345}
Did you see that value in a debugger, or is that the value you're trying to set expiration to (if the latter, the DateTime would've truncated to {09:48:47.6720000}, hence the value you see in the database).

I managed to solve my problem. In SQL datetime millisecond values are truncated.

DateTimeFormat issue when pass the parameter to MS-Sql stored procedure

I have a stored procedure, which has a parameter like #CurrentDate datetime, when I pass the value DateTime.Now from the front end (C#) to this stored procedure it is working fine.
But when I change the Date Format as English(India) in my system/server, that time DateTime.Now will return a value like 25-10-2012 PM 05:23:27. I am passing this value to stored procedure and I'm getting an error message like the following,
Msg 242, Level 16, State 3, Line 10
The conversion of a varchar data type to a datetime data type resulted in an out-of-range value.
Note : I don't want to use GETDATE() from Sqlserver, I want to pass the parameter from c#.
How can I solve this?

The problem with the date format is because you are converting it to a string and then back to a DateTime value. Depending on the culture settings on the specific server this may or may not work. It may also misinterpret the data, e.g. transforming a date from 2013-10-12 to 2013-12-10.
DateTime datet = new DateTime(year,month,day);
startDateParam.Value = datet;
endDateParam.Value = datet;
"note that the server stored datetime with format '1900-01-01 00:00:00.000'"

You can use this conversion from C#. Hope this helps
DateTime.Now.ToString(DateTimeFormatInfo.InvariantInfo)

You will need to convert the value to a valid DateTime using Convert function.
For more information : http://www.sql-server-helper.com/tips/date-formats.aspx

Storing dates in local timezones can cause headache when you launch internationally.
If you save current date using GETUTCDATE() on SQL Server side, you can get the time in user specific timezone as follows:
public DateTime GetDateByTimeZoneId(DateTime dateTime, string timeZone)
{
if (dateTime == null)
{
return null;
}
dateTime = DateTime.SpecifyKind(dateTime, DateTimeKind.Utc);
return TimeZoneInfo.ConvertTimeFromUtc(dateTime, TimeZoneInfo.FindSystemTimeZoneById(timeZone));
}
You can then pass user relevant timezone like "GMT Standard Time"

SqlDateTime overflow, but I want a NULL or MinValue

On this project, I am tracking when something is created, edited, and finally processed. I have three DateTime fields setup for this. The code below is for when I create the record.
newsArchive.CreateDateTime = DateTime.Now;
newsArchive.ModifyDateTime = DateTime.MinValue;
newsArchive.SendDateTime = DateTime.MinValue;
naRepository.Add(newsArchive);
naRepository.Save();
I am getting "SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM." when I try to add it. I know I can't send a NULL. How would you handle this?
I am using Linq2SQL to process this.

Why can't you send a null? AFAIK, Linq2SQL supports nullable value types; you just need the column in the DB to be nullable or L2S won't project the DAO with the nullable type.
You could use (DateTime)(SqlDateTime.MinValue) instead of DateTime.MinValue. This will use the minimum SQL-compatible datetime value, explicitly cast to DateTime.
Though both SqlDateTime and DateTime actually store time as a UInt64 "Ticks" value, the difference between the two types is that SQL Server uses a different epoch (value for zero) and a different resolution (what 1 "tick" represents in fractions of a second) than the CLR's DateTime.

Which version of SQL Server are you using? If you are using SQL 2008 (or 2008 R2) you can use the datetime2 data type which can support the full range of the .NET DateTime type.
Otherwise, use NULL (your model will need to have a property of type Nullable<DateTime>) or live within the limitations of the data type and DateTime.MinValue exceeds the limit of the SQL datetime type.

Create your own minimum date - a Date variable with value 1/1/1753 12:00:00 AM and use that instead of DateTime.MinValue

The datetime2 datatype allows dates as early as year 1. You can also use DateTime? to allow null dates in your .net code

Entity framework problem: How to handle errored column

I'm using ado.net entity data model. When update entity object, this error shown "String or binary data would be truncated" or "SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.". I know why this error shown.
How to handle this error created on which column ?

You probably have an uninitialized DateTime property on your object. The default value, which is in the year 0, cannot be stored in SQL Server's weirdly limited DATETIME columns. Set the property to a reasonable value or make it nullable in your DB.

In addition to Craig you could set both - the db-field and the variable - to nullable. Might be a bit more performant.

1/1/0001 12:00:00 AM not Updating SQL 2008 Date field

this is just weird and is giving me a headache. I looked over my code and I don't see any logical errors causing it.
Any other date set to my birthDate DateTime variable in my class works when I add it as the value in my conn.AddParam, but when I send back 1/1/0001 12:00:00 AM (which was sent by setting it to MinValue) to SQL 2008's Date field, it remains the default which I have set to null in the databse for that field:
conn.AddParam("#birthDate", birthDate);
birthDate is type DateTime. It's set to DateTime.MinValue; I don't see why it wouldn't take this.

I may not be understanding the question, but I believe January 1, 1753 is the earliest date supported by SQL Server.
Source

If you need to go back that far, use DateTime2. It allows you to go back as far as 1/1/0001 http://technet.microsoft.com/en-us/library/bb677335.aspx

Just a guess but it might be caused by a casting issue. Since your birthDate variable has a time component (12:00 AM), SQL might be casting it to a DateTime before its inserted into the Date field. Since 1/1/0001 is an invalid SQL DateTime it might be having problems. Try setting your #birthDate parameter to birthDate.Date instead.

In SQL server 2008 :
Date data type : - will allow you to store only date (YYYY-MM-DD) and as range 0001-01-01 through 9999-12-31.Its accurate to 1 day
Time data type : It stores in the format hh:mm:ss:nnnnnnn , with range 00:00:00.0000000 through 23:59:59:9999999 and is accurate to 100 nanoseconds
DateTime2 : the format is YYYY-MM_DD hh:mm:ss:nnnnnnnm with a range 0001-01-01 00:00:00.0000000 through 999-12-31:59 9999999,accuracy is 100 nano seconds
DateTimeOffset:It includes additional information to track the time zone.The format is YYYY-MM-DD hh:mm:ss[.nnnnnnn][+/-]hh:mm with a range of 0001-01-01 00:00:00.000000 through 9999-12-31 23:59:50.9999999.storage 8 yo 10 bytes.

DateTime is a value type. Therefore if a DateTime variable hasn't been assigned it's value would be the default one which happens to be DateTime.MinValue. That's why when you explicitly set your birthDate to DateTime.MinValue it's treated as it was not assigned at all (e.g. as null) and thus gets replaced by the default value for that parameter in your stored proc.