Programming Forums > Application Development > C#

hoffmandirt · May 15th, 2006, 9:09 AM

Does anyone happen to know off hand what the default value of a freshly instantiated System.DateTime value is? I always thought a DateTime value could be set to null but when I place checks for null, I receive warnings saying that it is unreachable code. So that also makes me wonder how you guys go about validating date/times.

Ooble · May 15th, 2006, 1:11 PM

I set them to 0001-01-01 00:00:00 manually on creation (new DateTime(1, 1, 1);), and compare them against that.

Booooze · May 15th, 2006, 1:11 PM

Hmm. I have yet to actually validate or compare times, but I thought you had to use some other method or property with it. I been using System.DateTime. Now and .Year , month etc. DateTime is a type. Is it actually possible to have it set to null?

Ooble · May 15th, 2006, 1:32 PM

I believe it is possible to set it to null - try it and see. If it is, I've been killing my processor without a reason.

hoffmandirt · May 15th, 2006, 3:14 PM

I thought it was possible to, but I tried it and it is not.

"Error 1 Cannot convert null to 'System.DateTime' because it is a value type."

Kaja Fumei · May 15th, 2006, 3:39 PM

DateTime is a value type (therefore a struct) and structs can not normally be null. However there is a way in C# 2.0 to overcome this. Put a ? after the value type name and it will be nullable:

(Toggle Plain Text)

System.DateTime? time = null;
int? x = null;
float? f = null;

However, there is no way to set a value type to null before C# 2.0

hoffmandirt · May 15th, 2006, 3:41 PM

I haven't had time to check, but I am curious to know if its default value is System.DateTime.MinValue.

BlazingWolf · May 15th, 2006, 5:33 PM

A quick check... 1/1/0001 12:00:00 AM

I'm thinking theres a better way to do what your trying to do though.

Booooze · May 16th, 2006, 1:09 AM

Quote:

Originally Posted by hoffmandirt

I thought it was possible to, but I tried it and it is not.

"Error 1 Cannot convert null to 'System.DateTime' because it is a value type."

That's what I figured. Like I said, I haven't had this problem, because I always set it to some date.

May 15th, 2006, 9:09 AM	#1
hoffmandirt Hobbyist Programmer Join Date: Jul 2005 Location: PA Posts: 125 Rep Power: 4	System.DateTime default value. Does anyone happen to know off hand what the default value of a freshly instantiated System.DateTime value is? I always thought a DateTime value could be set to null but when I place checks for null, I receive warnings saying that it is unreachable code. So that also makes me wonder how you guys go about validating date/times.

May 15th, 2006, 1:11 PM	#2
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	I set them to 0001-01-01 00:00:00 manually on creation (new DateTime(1, 1, 1);), and compare them against that. __________________ Me :: You :: Them

May 15th, 2006, 1:32 PM	#4
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	I believe it is possible to set it to null - try it and see. If it is, I've been killing my processor without a reason. __________________ Me :: You :: Them

May 15th, 2006, 3:39 PM	#6
Kaja Fumei Hobbyist Programmer Join Date: Oct 2005 Posts: 134 Rep Power: 4	DateTime is a value type (therefore a struct) and structs can not normally be null. However there is a way in C# 2.0 to overcome this. Put a ? after the value type name and it will be nullable: (Toggle Plain Text) System.DateTime? time = null; int? x = null; float? f = null; System.DateTime? time = null; int? x = null; float? f = null; However, there is no way to set a value type to null before C# 2.0

May 15th, 2006, 5:33 PM	#8
BlazingWolf Hobbyist Programmer Join Date: Sep 2004 Posts: 207 Rep Power: 5	A quick check... 1/1/0001 12:00:00 AM I'm thinking theres a better way to do what your trying to do though. __________________ _______________________________ BlazingWolf

May 15th, 2006, 1:11 PM	#3
Booooze Expert Programmer Join Date: Mar 2006 Location: Igloo Posts: 710 Rep Power: 3	Hmm. I have yet to actually validate or compare times, but I thought you had to use some other method or property with it. I been using System.DateTime. Now and .Year , month etc. DateTime is a type. Is it actually possible to have it set to null?

May 15th, 2006, 3:14 PM	#5
hoffmandirt Hobbyist Programmer Join Date: Jul 2005 Location: PA Posts: 125 Rep Power: 4	I thought it was possible to, but I tried it and it is not. "Error 1 Cannot convert null to 'System.DateTime' because it is a value type."

May 15th, 2006, 3:41 PM	#7
hoffmandirt Hobbyist Programmer Join Date: Jul 2005 Location: PA Posts: 125 Rep Power: 4	I haven't had time to check, but I am curious to know if its default value is System.DateTime.MinValue.

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Programming Forums > Application Development > C#

System.DateTime default value.