C# array access issue

Question

I am using Asp.net/C# ,, i have declared an integer array as follows public int[] recno; As i dont know the exact size of the array ,, however inside a function i get to know its size based on the number of customer_id's in the table.Here is the function

public void GetRecordNo()
        {
            recid = from id in dt.cust_masters
                    select id;
            recno = new int[recid.Count()];

            for (int i = 0; i < recid.Count(); i++)
            {
                recno[i] = Convert.ToInt32(recid.ElementAt(i).customer_id);
            }

        }

When i try to call a function ShowRecord(int index) which accepts the id of the customer in the following manner

ShowRecord(recno[0])

It gives me an error

Object reference not set to an instance of an object.

Can anybody point me where am i going wrong. Thanks

@Maheep it does return value because when i call the function ShowRecord() inside that function it works well .. — Priyank Patel
– Priyank Patel, Commented Mar 14, 2012 at 9:06
@KOL it gives me the same error , which i mentioned in the question — Priyank Patel
– Priyank Patel, Commented Mar 14, 2012 at 9:09

Henk Holterman · Accepted Answer · 2012-03-14 09:08:31Z

3

You can simplify your code:

recid = from id in dt.cust_masters
          select id.customer_id;

//recno = new int[recid.Count()];
recno = recid.ToArray();
// remove for-loop

And to find/prevent your null ref problem:

void  ShowRecord(int index)
{
    if (index < 0 || index >= recno.Length)
       throw new InvalidArgumentException("index");

    var id = recno[index];
    ...
}

answered Mar 14, 2012 at 9:08

Henk Holterman

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3 Comments

Priyank Patel Over a year ago

,,,, but will that allow me to access values of recno outside that function

Henk Holterman Over a year ago

That depends on how public / private you make recno[]. Not on this method. But what is the actual question ?

Priyank Patel Over a year ago

,, i have made it public , my question is that i need the values of the array to be passed as parameters to ShowRecord() function.

Arion · Accepted Answer · 2012-03-14 09:09:45Z

3

Why can you just use:

public void GetRecordNo()
{
    var recno=(
        from id in dt.cust_masters
        select id.customer_id
    ).ToArray();
}

answered Mar 14, 2012 at 9:09

Arion

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1 Comment

Priyank Patel Over a year ago

then how do i pass id's to my function

Botz3000 · Accepted Answer · 2012-03-14 09:22:38Z

1

First check which object is null by setting a breakpoint and hovering over the parameter recno of ShowRecord(recno[0]). Is it null? If yes, make sure your GetRecordNo() method is actually being called before your call to ShowRecord.

Or use this to access recno:

public int[] RecNo {
    get {
        if (recno == null) { GetRecNo(); }
        return recno;
    }
}

and then use it like

ShowRecord(RecNo[0])

edited Mar 14, 2012 at 9:22

answered Mar 14, 2012 at 9:16

Botz3000

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7 Comments

Priyank Patel Over a year ago

,, i call GetRecordNo() on load and im calling ShowRecord on click of a button , do you think this might be issue.

Priyank Patel Over a year ago

the issue was exactly what you pointed out ,,, when i called GetRecordNo() and then ShowRecord() ,, it worked fine ,,, so will i have to call it again n again ...Thanks

Botz3000 Over a year ago

@freebird Maybe you are accessing a local variable rather than your public field? I edited my post, maybe it helps.

Priyank Patel Over a year ago

thanks a lot it worked well for me ,,,, if you could do a favour , could you please explain me how it works.Thanks

Botz3000 Over a year ago

It checks if recno is null, and if it is, it calls GetRecNo(). That way, if you access the property RecNo, you never get null. But i think that your load method (where you said you call GetRecNo()) might not get called if recno is still null at this point.

|

user1082916 · Accepted Answer · 2012-03-14 09:18:26Z

0

I think, ShowRecord(int index) contains a parameter which includes int index but when you are calling function,you are using ShowRecord(recno[0]) which means you are passing recno record at index 0.......

answered Mar 14, 2012 at 9:18

user1082916

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