Why is System.DateTime a structure?

[Pram]

I am curious why did Microsoft write System.DateTime as a structure instead
of a class?

Maybe for backward compatibilty with any existing old code?

FYI, one of the differences between structure and class is we can set the
structure to Nothing.

[Pram]

Sorry it should be:
one of the differences between structure and class is we can NOT set the
structure to Nothing.

"Pram" <pr**@nospam.com> wrote in message
news:uw**************@TK2MSFTNGP09.phx.gbl...

I am curious why did Microsoft write System.DateTime as a structure instead of a class?

Maybe for backward compatibilty with any existing old code?

FYI, one of the differences between structure and class is we can set the
structure to Nothing.

[Jay B. Harlow [MVP - Outlook]]

Pram,
I believe DateTime is a structure, as it meets all the criteria to use when
deciding to make a type a Structure as set forth by the .NET Design
Guidelines for Class Library Developers, in that it:

- Acts like a primitive type
- It has an instance size of under 16 bytes
- It is immutable
- It has value semantics.

Which is 4 for 4!

http://msdn.microsoft.com/library/de...guidelines.asp

The one item that is not listed, but is implied by the above list is as a
Structure it is significantly easier to work with as opposed to being a
class!

Hope this helps
Jay

"Pram" <pr**@nospam.com> wrote in message
news:uw**************@TK2MSFTNGP09.phx.gbl...

I am curious why did Microsoft write System.DateTime as a structure instead of a class?

Maybe for backward compatibilty with any existing old code?

FYI, one of the differences between structure and class is we can set the
structure to Nothing.

[Jeff Callahan]

Hi Pram,

The key difference between structs, which are value types, and Classes,
which are reference types, is how they are allocated in memory. A struct
is allocated directly on the stack and a Class is allocated on the run-time
heap. This distinction allows them to be used in different ways and
perhaps most importantly it allows the runtime to treat them in different
ways. For a good discussion of this, check out the following MSDN page:

ms-help://MS.MSDNQTR.2003FEB.1033/vbls7/html/vblrfVBSpec6_1.htm

or if you do not have MSDN, you can check it out on the web at:
http://msdn.microsoft.com/library/de...us/vbls7/html/
vblrfvbspec6_1.asp

Another good (and more thorough) explanation:

http://www.yoda.arachsys.com/csharp/memory.html

Let me know if you still have any questions about this.

Jeff.

--

This posting is provided "AS IS" with no warranties, and confers no rights.
Use of included script samples are subject to the terms specified at
http://www.microsoft.com/info/cpyright.htm

Note: For the benefit of the community-at-large, all responses to this
message are best directed to the newsgroup/thread from which they
originated.

[Pram]

Jeff,
I do understand the benefits of structure over class.

The reason I asked that question because I have an XML string that has an
empty date element.
Then when I do "XML Serialization into an object", I get an exception
because dateTime structure
does not allow Null or Nothing. I have not found a nice way or trick to
solve this problem yet.

Thanks Jeff.

"Jeff Callahan" <Je*****@online.microsoft.com> wrote in message
news:tj**************@cpmsftngxa06.phx.gbl...

Hi Pram,

The key difference between structs, which are value types, and Classes,
which are reference types, is how they are allocated in memory. A struct
is allocated directly on the stack and a Class is allocated on the run-time heap. This distinction allows them to be used in different ways and
perhaps most importantly it allows the runtime to treat them in different
ways. For a good discussion of this, check out the following MSDN page:

ms-help://MS.MSDNQTR.2003FEB.1033/vbls7/html/vblrfVBSpec6_1.htm

or if you do not have MSDN, you can check it out on the web at:
http://msdn.microsoft.com/library/de...us/vbls7/html/ vblrfvbspec6_1.asp

Another good (and more thorough) explanation:

http://www.yoda.arachsys.com/csharp/memory.html

Let me know if you still have any questions about this.

Jeff.

--

This posting is provided "AS IS" with no warranties, and confers no rights. Use of included script samples are subject to the terms specified at
http://www.microsoft.com/info/cpyright.htm

Note: For the benefit of the community-at-large, all responses to this
message are best directed to the newsgroup/thread from which they
originated.