C# Discussion Boards - CodeProject

tashee22-Dec-12 5:22

22-Dec-12 5:22

Hello,

I have declared a null array but when i try to use this array to store my values, it gives me an error as "use of unassigned local variable".
I donno whats wrong.
here is my code

double[] strPLatitude;
if (dr.HasRows)
{
while (dr.Read())
{
strPLatitude[i] = Convert.ToDouble(dr["latitude"].ToString());
i++;
}
}

Re: error i declaring null arrays

Richard MacCutchan22-Dec-12 6:40

Richard MacCutchan

22-Dec-12 6:40

You must allocate some space to it before you can store anything in it. Something like:

if (dr.HasRows)
{
    strPLatitude = new double[N]; // where N is the number of items to be stored.
    while (dr.Read())
    {

You are also incrementing the variable i; are you sure you initialised it somewhere?

One of these days I'm going to think of a really clever signature.

Re: error i declaring null arrays

tashee22-Dec-12 7:39

tashee

22-Dec-12 7:39

Yes i have initialized variable i

And data in my database table would increase with time. hence it's not possible to allocate a space to the array, since i don't know how much records exist in my table

Re: error i declaring null arrays

PIEBALDconsult22-Dec-12 8:11

PIEBALDconsult

22-Dec-12 8:11

Then use a List or something. We tend not to use arrays in C#.

Re: error i declaring null arrays

harold aptroot24-Dec-12 0:52

harold aptroot

24-Dec-12 0:52

Actually, you do know what's wrong: you're using an unassigned local variable. It will even tell you that strPLatitude is the culprit.
How to fix? Assign something to it, obviously. Most C# compile errors are easy like that.

You wanted a null array? Then make a null array: double[] strPLatitude = null;

That doesn't make the code work, I grant you, but it fixes this problem.

However, this:

tashee wrote:
declared a null array but when i try to use this array to store my values

Reveals a deeper problem. You can't use something that doesn't exist. Like Richard wrote, "You must allocate some space to it before you can store anything in it". Your reply to him seems to imply you didn't really get it.

This is like saying "I have a place where a bookshelf should go but there isn't one there yet, why do things go wrong when I try to store books in it?"

Don't use something that doesn't exist. You need an actual bookshelf, not just a place where a bookshelf could go.

PIEBALDconsult suggest you use a List, you should probably do that. Be sure to Add[^] the items to the list, don't try to stuff them into positions that do not exist.

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