Set an empty DateTime variable
C#SqlDatetimeC# Problem Overview
I would declare an empty String variable like this:
string myString = string.Empty;
Is there an equivalent for a 'DateTime' variable ?
Update :
The problem is I use this 'DateTime' as a parameter for a 'StoredProcedure' in SQL. E.g:
DateTime? someDate = null;
myCommand.Parameters.AddWithValue("@SurgeryDate", someDate);
When I run this code an exception is catched telling me the 'StoredProcedure' expected a '@SurgeryDate' parameter. But i provided it. Any idea why?
C# Solutions
Solution 1 - C#
Since DateTime
is a value type you cannot assign null
to it, but exactly for these cases (absence of a value) Nullable<T>
was introduced - use a nullable DateTime
instead:
DateTime? myTime = null;
Solution 2 - C#
No. You have 2 options:
DateTime date = DateTime.MinValue;
This works when you need to do something every X amount of time (since you will always be over MinValue
) but can actually cause subtle errors (such as using some operators w/o first checking if you are not MinValue
) if you are not careful.
And you can use Nullable
:
DateTime? date = null;
Which is nice and avoids most issues while introducing only 1 or 2.
It really depends on what you are trying to achieve.
Solution 3 - C#
You can set a DateTime variable to be '1/1/0001 00:00:00' but the variable itself cannot be null. To get this MinTime use:
DateTime variableName = DateTime.MinValue;
Solution 4 - C#
You may want to use a nullable datetime. Datetime? someDate = null;
You may find instances of people using DateTime.Max
or DateTime.Min
in such instances, but I highly doubt you want to do that. It leads to bugs with edge cases, code that's harder to read, etc.
Solution 5 - C#
The method you used (AddWithValue
) doesn't convert null
values to database nulls. You should use DBNull.Value
instead:
myCommand.Parameters.AddWithValue(
"@SurgeryDate",
someDate == null ? DBNull.Value : (object)someDate
);
This will pass the someDate
value if it is not null
, or DBNull.Value
otherwise. In this case correct value will be passed to the database.
Solution 6 - C#
Either:
DateTime dt = new DateTime();
or
DateTime dt = default(DateTime);
Solution 7 - C#
If you set the date to
DateTime dNewDate = new DateTime();
The value is set to {1/1/0001 12:00:00 AM}
Solution 8 - C#
Option 1: Use a nullable DateTime?
Option 2: Use DateTime.MinValue
Personally, I'd prefer option 1.
Solution 9 - C#
A string
is a sequence of characters. So it makes sense to have an empty string
, which is just an empty sequence of characters.
But DateTime
is just a single value, so it's doesn't make sense to talk about an “empty” DateTime
.
If you want to represent the concept of “no value”, that's represented as null
in .Net. And if you want to use that with value types, you need to explicitly make them nullable. That means either using Nullable<DateTime>
, or the equivalent DateTime?
.
DateTime
(just like all value types) also has a default value, that's assigned to uninitialized fields and you can also get it by new DateTime()
or default(DateTime)
. But you probably don't want to use it, since it represents valid date: 1.1.0001 0:00:00.
Solution 10 - C#
There's no such thing as an empty date per se, do you mean something like:
DateTime? myDateTime = null;
Solution 11 - C#
The .addwithvalue needs dbnull. You could do something like this:
DateTime? someDate = null;
//...
if (someDate == null)
myCommand.Parameters.AddWithValue("@SurgeryDate", DBnull.value);
or use a method extension...
public static class Extensions
{
public static SqlParameter AddWithNullValue(this SqlParameterCollection collection, string parameterName, object value)
{
if (value == null)
return collection.AddWithValue(parameterName, DBNull.Value);
else
return collection.AddWithValue(parameterName, value);
}
}
Solution 12 - C#
This will work for null able dateTime parameter
. .
SearchUsingDate(DateTime? StartDate, DateTime? EndDate){
DateTime LastDate;
if (EndDate != null)
{
LastDate = (DateTime)EndDate;
LastDate = LastDate.AddDays(1);
EndDate = LastDate;
}
}