Unable to declare an ArrayList

Question

I'm not able to declare an ArrayList. Here's my code. (I'd much rather use Lists, but I'm just trying to understand the concept of an ArrayList).

private void button1_Click(object sender, EventArgs e)
{
    ArrayList salesTotals = new ArrayList();
    decimal[] decimalSales = { 1000m, 2000m, 3000m };

    foreach (decimal singleSales in decimalSales)
    {
        salesTotals.Add(singleSales);
    }
}

When I compile this, I get this error:

'ArrayList' is a 'namespace' but is used like a 'type'

I'm using the namespace System.Collections (not .Generic)

What is causing this and how do I fix it?

Silly question, but did you accidently name your class `ArrayList`? — George Johnston, Jul 01 '11 at 20:00
maybe your example code is in namespace that you called ArrayList? Could you try writing explicitly System.Collections.ArrayList in your code? — Paolo Falabella, Jul 01 '11 at 20:03
If you have enough time, read [this interesting answer](http://stackoverflow.com/questions/2046012/companyname-foo-is-a-namespace-but-is-used-like-a-type/2330632#2330632) from Eric Lippert about a similar question. — Tim Schmelter, Jul 01 '11 at 20:20

score 6 · Answer 1 · answered Jul 01 '11 at 20:01

6

One of the namespaces in your project is ArrayList. This is causing the conflict.

Try changing the namespace, or fully qualifying it like this:

System.Collections.ArrayList salesTotals = new System.Collections.ArrayList ();

answered Jul 01 '11 at 20:01

agent-j

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mdm · Accepted Answer · 2011-07-01T20:05:31.863

3

It sounds like you are using the ArrayList within a namespace itself called ArrayList. The symbol is resolving to the namespace definition, which is invalid in the symbol's context, causing the error you describe.

edited Jul 01 '11 at 20:05

answered Jul 01 '11 at 20:00

mdm

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2

sigh... I just proved my absolute "newbness". In visual studio, since I was trying to test a basic ArrayList, I called the project "ArrayList", which resulted in using a namespace with the same name. Thanks for pointing this out @mdm. – Ray Jul 01 '11 at 20:03
No worries, it happens to the best of us :-) – mdm Jul 01 '11 at 20:03

score 1 · Answer 3 · answered Jul 01 '11 at 20:02

1

Cause you have a namespace defined with the name ArrayList. Change the namespace name to something different.

answered Jul 01 '11 at 20:02

Rahul

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score 0 · Answer 4 · edited Mar 18 '17 at 03:33

0

In my case I was saved the project name as ArrayList and when I was using ArrayList then it tells ArrayList is only namespace but not a type.

After changing the project name, now I am able to use ArrayList as a type. If you have taken the project name as ArrayList then you should have to change it to another name, I'm sure it will definitely work!

edited Mar 18 '17 at 03:33

Divyang Desai

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answered Mar 18 '17 at 02:46

Piyush Kumar

11
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score 0 · Answer 5 · answered Sep 21 '18 at 04:07

0

error is depend on .net core version. Path is right click on project=> Properties => choose .net core version in target framework. Arraylist cannot use in lower .net core version.

answered Sep 21 '18 at 04:07

Zuu May Khin Ei

1

score 0 · Answer 6 · answered Jul 01 '11 at 20:01

0

Is your project called ArrayList? That would do it. The compiler is finding a namespace called ArrayList. Try fully qualifying it ie new System.ArrayList();

answered Jul 01 '11 at 20:01

therealmitchconnors

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It would be `System.Collections.ArrayList()`. – mdm Jul 01 '11 at 20:04

Unable to declare an ArrayList

6 Answers6