How to test if variable is assigned?

Posted on 2003-12-08
Last Modified: 2008-03-06
System.DateTime d;

How do you test if the variable d has been assigned?

What about

int i;


Question by:baltmann
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions

Expert Comment

ID: 9895490
LVL 19

Expert Comment

ID: 9895554
as far as i understood..

int i;
if (i!=null) // if the variable has been assigned

Author Comment

ID: 9895811
The compile errors are:

with DateTime:

System.DateTime dt ;
if(dt != null)
Operator '!=' cannot be applied to operands of type 'System.DateTime' and '<null>'

with int:
int i;
Operator '==' cannot be applied to operands of type 'int' and '<null>'

LVL 20

Accepted Solution

TheAvenger earned 50 total points
ID: 9896285
An object is checked with o != null. Objects are strings, forms, arraylists, etc. However DateTime and int are value types, which means they cannot be compared to null.

So you have to implement your own logic. For example if you need only positive numbers you can do like this:

int i = -1;
if (i < 0)
  // still no real value
  // ok

For DateTime you can make:
DateTime dt = DateTime.MinValue;
if (dt == DateTime.MinValue)
  // still no real value
  // ok

Assisted Solution

jj819430 earned 50 total points
ID: 9897533
int i;
bool iSet = false;

// whenever you set i, set iSet = true;

//your int has been set
//your int has not been set

All the others were just as valid a way of doing this, because they do not require the added overhead. I  like this approach only because it doesn't limit the functionality of the int. If you will only be using positive or only be using negative numbers I would suggest you use "TheAvenger"'s approach for the speed. If you need both Positive and Negative integer values, then this may be your best approach.

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Article by: Najam
Having new technologies does not mean they will completely replace old components.  Recently I had to create WCF that will be called by VB6 component.  Here I will describe what steps one should follow while doing so, please feel free to post any qu…
We all know that functional code is the leg that any good program stands on when it comes right down to it, however, if your program lacks a good user interface your product may not have the appeal needed to keep your customers happy. This issue can…
NetCrunch network monitor is a highly extensive platform for network monitoring and alert generation. In this video you'll see a live demo of NetCrunch with most notable features explained in a walk-through manner. You'll also get to know the philos…
Do you want to know how to make a graph with Microsoft Access? First, create a query with the data for the chart. Then make a blank form and add a chart control. This video also shows how to change what data is displayed on the graph as well as form…

726 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question