Why am I getting a NullReferenceException with this code?

Question

I have this code here in my program:

foreach (HtmlElement chat in wb.Document.GetElementsByTagName("input"))
{
    if (chat != null)
    {
        if (chat.InnerText.Equals("Chat"))
        {
            chat.InvokeMember("Click");
            loggedIn = true;
            break;
        }
    }
}

Once it gets to the if(chat.InnerText.Equals("Chat")) it throws a NullReferenceException Error as shown in the ScreenShot below:

Error Code

Does anyone know why it is giving me that? I even put the if (chat != null) code in there, and it still throws it.

This is the website code:

<div class="ContentTab">
    Chat
</div>

chat could be an autoclosing tag, then have no inner text. Dunno :D — Kilazur, Jul 09 '14 at 13:03
The use of `Equals()` in this context looks like a Java-ism. Use the equality operator instead, so you won't end up invoking a method on a `null` reference. — Frédéric Hamidi, Jul 09 '14 at 13:05

Michael B · Answer 1 · 2017-02-09T10:09:02.333

2

Chat.InnerText is null, even though Chat isn't. Try this:

foreach (HtmlElement chat in wb.Document.GetElementsByTagName("input"))
{
        if (chat != null && chat.InnerText != null && chat.InnerText.Equals("Chat"))
        {
            chat.InvokeMember("Click");
            loggedIn = true;
            break;
        }
}

edited Feb 09 '17 at 10:09

answered Jul 09 '14 at 13:00

Michael B

581
1
5
17

Trying that... Thanks – Jack Nelson Jul 09 '14 at 13:03
Didn't work... This is the website code: `
Chat
` Do you know how to click it? Because that code isn't working. – Jack Nelson Jul 09 '14 at 13:05
You still got the null reference exception? – Michael B Jul 09 '14 at 13:06
No, I didn't get the error, but it doesn't click... – Jack Nelson Jul 09 '14 at 13:08
So it did solve the issue you asked about. You are now onto a different issue... It didn't click because InnerText is null so it wouldn't fail the if condition – Michael B Jul 09 '14 at 13:09
Yes... Do you know how to get it to click? – Jack Nelson Jul 09 '14 at 13:11
@JackNelson: Try to check for the class `ContentTab`: http://stackoverflow.com/questions/3436116/how-to-select-a-class-by-getelementbyclass-and-click-on-it-programmically – Will Marcouiller Jul 09 '14 at 13:12
There are like 10 different tabs, that are all called content tab... The only way to tell them apart is by the inner text – Jack Nelson Jul 09 '14 at 13:13

score 2 · Answer 2 · answered Jul 09 '14 at 13:00

2

The property InnerText of chat variable is null

answered Jul 09 '14 at 13:00

nraina

324
2
20

score 1 · Answer 3 · answered Jul 09 '14 at 13:01

1

try

    if (chat.InnerText == "Chat")
    {
        chat.InvokeMember("Click");
        loggedIn = true;
        break;
    }

I believe that .Equals checks object similarity, and operator == checks reference equality.

answered Jul 09 '14 at 13:01

JKennedy

18,150
17
114
198

1

Strings are a special case. `==` compares them by value, not by reference, even though they're reference types. – Frédéric Hamidi Jul 09 '14 at 13:06

score 1 · Answer 4 · answered Jul 09 '14 at 13:04

you can try checking the object itself its empty try this

foreach (HtmlElement chat in wb.Document.GetElementsByTagName("input"))
{
    if (chat != null && (!chat.isEmpty())&& chat!="")
    {
        if (chat.InnerText.Equals("Chat"))
        {
            chat.InvokeMember("Click");
            loggedIn = true;
            break;
        }
    }
}

Why am I getting a NullReferenceException with this code?

4 Answers4