C# - NullReferenceException was unhandled

[AlTech]

For the life of me, I don't know what i'm doing wrong.

 

It's telling me that I've got a NullReferenceException. Which would mean that one of my variables has no value (is null) but that doesn't make any sense since all of mine have values.

 

 class OnTask
    {
        Dialog DialogBox = new Dialog();

        public string URL;
        public bool IsOnTask;


        public string[] OnTask_AllowedWebsites = new string[14];
        public string[] OnTask_NotAllowedWebsites = new string[22];
        public string[] OnTask_AllowedExtension = new string[9];

        //Check if the website is in the allowed list
        public void AllowedCheck()
        {
            OnTask_AllowedWebsites[0] = "onedrive.com";
            OnTask_AllowedWebsites[1] = "google.com";
            OnTask_AllowedWebsites[2] = "icloud.com";
            OnTask_AllowedWebsites[3] = ".edu";
            OnTask_AllowedWebsites[4] = ".org";
            OnTask_AllowedWebsites[5] = "youtube.com";
            OnTask_AllowedWebsites[6] = "dropbox.com";
            OnTask_AllowedWebsites[7] = "microsoft.com";
            OnTask_AllowedWebsites[8] = "bing.com";
            OnTask_AllowedWebsites[9] = "gmail.com";
            OnTask_AllowedWebsites[10] = "linkedin.com";
            OnTask_AllowedWebsites[11] = "stackoverflow.com";
            OnTask_AllowedWebsites[12] = "slack.com";

            if (URL == OnTask_AllowedWebsites[0])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[1])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[2])
            {
                IsOnTask = true;

            }
            if (URL == OnTask_AllowedWebsites[3])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[4])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[5])
            {
                IsOnTask = true;

            }
            if (URL == OnTask_AllowedWebsites[6])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[7])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[8])
            {
                IsOnTask = true;

            }
            if (URL == OnTask_AllowedWebsites[9])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[10])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[11])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[12])
            {
                IsOnTask = true;
            }
            if (URL == OnTask_AllowedWebsites[13])
            {
                IsOnTask = true;
            }
        }
        public void NotAllowedCheck()
        {
            OnTask_NotAllowedWebsites[0] = "steampowered.com";
            OnTask_NotAllowedWebsites[1] = "hub";
            OnTask_NotAllowedWebsites[2] = "amazon.com";
            OnTask_NotAllowedWebsites[3] = "ebay.com";
            OnTask_NotAllowedWebsites[4] = "spotify.com";
            OnTask_NotAllowedWebsites[5] = "linustechtips.com";
            OnTask_NotAllowedWebsites[6] = "apple.com";
            OnTask_NotAllowedWebsites[7] = "xbox.com";
            OnTask_NotAllowedWebsites[8] = "wccftech.com";
            OnTask_NotAllowedWebsites[9] = "fake";
            OnTask_NotAllowedWebsites[10] = ".con";
            OnTask_NotAllowedWebsites[11] = ".cm";
            OnTask_NotAllowedWebsites[12] = "skype.com";
            OnTask_NotAllowedWebsites[13] = "ad";
            OnTask_NotAllowedWebsites[14] = "game";
            OnTask_NotAllowedWebsites[15] = "facebook.com";
            OnTask_NotAllowedWebsites[16] = "instagram.com";
            OnTask_NotAllowedWebsites[17] = "twitter.com";
            OnTask_NotAllowedWebsites[18] = "wikipedia.org";
            OnTask_NotAllowedWebsites[19] = "yahoo.com";
            OnTask_NotAllowedWebsites[20] = "tube";
            OnTask_NotAllowedWebsites[21] = "red";

            if (URL == OnTask_NotAllowedWebsites[0])
            {
                IsOnTask = false;
            }
            else if (URL == OnTask_NotAllowedWebsites[1])
            {
                IsOnTask = false;
            }
            else if (URL == OnTask_NotAllowedWebsites[2])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[3])
            {
                IsOnTask = false;

            }
            else if (URL == OnTask_NotAllowedWebsites[4])
            {
                IsOnTask = false;
            }
            else if (URL == OnTask_NotAllowedWebsites[5])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[6])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[7])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[8])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[9])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[10])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[11])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[12])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[13])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[14])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[15])
            {
                IsOnTask = false;

            }
           else if (URL == OnTask_NotAllowedWebsites[16])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[17])
            {
                IsOnTask = false;

            }
           else if (URL == OnTask_NotAllowedWebsites[18])
            {
                IsOnTask = false;
            }
           else if (URL == OnTask_NotAllowedWebsites[19])
            {
                IsOnTask = false;
            }
            else if (URL == OnTask_NotAllowedWebsites[20])
            {
                IsOnTask = false;
            }
            else if (URL == OnTask_NotAllowedWebsites[21])
            {
                IsOnTask = false;
            }
        } 
        public void AllowedExtension()
        {
            OnTask_AllowedExtension[0] = ".edu";
            OnTask_AllowedExtension[1] = ".org";
            OnTask_AllowedExtension[2] = ".com";
            OnTask_AllowedExtension[3] = ".lithium";
            OnTask_AllowedExtension[4] = ".html";
            OnTask_AllowedExtension[5] = ".com";
            OnTask_AllowedExtension[6] = ".info";
            OnTask_AllowedExtension[7] = ".net";
            OnTask_AllowedExtension[8] = ".aspx";

            if (URL.EndsWith(OnTask_AllowedExtension[0]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[1]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[2]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[3]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[4]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[5]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[6]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[7]))
            {
                IsOnTask = true;
            }
            else if (URL.EndsWith(OnTask_AllowedExtension[8]))
            {
                IsOnTask = true;
            }
            else
            {
                //Do nothing if we haven't picked up any bad URL exxtensions
            }
        }
        public void OnTask_TempNavigate()
        {
            
            //Check to see if the website we are visiting is Not Allowed
            NotAllowedCheck();

            //Check to see if the website we are visiting is Allowed
            AllowedCheck();

            //Check to see if the extension is allowed
            AllowedExtension();
        }
    }

Once this is run from an external class it returns a value in the form of a bool "IsOnTask".

 

Thanks guys .

[vanished]

Sorry but I have to ask; it's really been bothering me - why do you use a ton of if statements instead of a loop to check the allowed websites array?

[Murasaki]

I suggest optimizing the code first like Ryan said, you're just making it harder for yourself if you ask me.

 

I'd help you but I'm at work and coding on phone.. please no

 

[squirrl]

8 minutes ago, Ryan_Vickers said:

Sorry but I have to ask; it's really been bothering me - why do you use a ton of if statements instead of a loop to check the allowed websites array?

 

 

Even a loop is more than you need. indexOf will work just fine for this.

 

I'm also pretty confused the way this is going about things. Usually, you have a whitelist, and only allow things on the whitelist, a blacklist and allow everything except things from the blacklist. here you have both, but also 2 whitelists. 

From the look of things, the last check renders the first 2 useless as well. You say facebook.com is off task, then say anything that ends with .com is on task. 

[madknight3]

3 minutes ago, squirrl said:

Even a loop is more than you need. indexOf will work just fine for this.

True, although I think Contains would be better in this use case.

 

 

[vanished]

Just now, madknight3 said:

-

8 minutes ago, squirrl said:

-

10 minutes ago, ModuleLFS said:

-

 

oh no I knew this would happen... we've gone completely off topic  

Do any of you know how to solve the actual problem?

 

(I'm sorry I brought up the loop thing, I knew it was a bad idea  )

[squirrl]

Anyway, as to @AluminiumTech's original question

 

if (URL == OnTask_AllowedWebsites[13])
            {
                IsOnTask = true;
            }

You never assign anything to [13] so you do have null variables.

[madknight3]

30 minutes ago, Ryan_Vickers said:

 

oh no I knew this would happen... we've gone completely off topic  

Do any of you know how to solve the actual problem?

 

(I'm sorry I brought up the loop thing, I knew it was a bad idea  )

Not completely true. Changing how he did the lookup would have also fixed the original issue that squirrl just pointed out.

 

edit: My mistake, it's fine for string[] to contain null and it's also fine to compare strings against null so this isn't the issue. It's possible the OP could use OnTask_AllowedWebsites[13] in another place and trigger a NullReferenceException though.

[vanished]

Just now, madknight3 said:

Not completely true. Changing how he did the lookup would have also fixed the original issue that @squirrl just pointed out.

hm, I suppose that's true if that really is the issue...

@AluminiumTech did he solve it?

[squirrl]

6 minutes ago, madknight3 said:

True, although I think Contains would be better in this use case.

 

 

 

 

 

 

There is no Array.Contains method. (You're probably thinking of string.contains)

IndexOf would just be 

if  (OnTaskNotAllowedWebsites.IndexOf(URL) != -1) {
// URL matches one of the websites
}

 

[AlTech]

10 minutes ago, squirrl said:

Anyway, as to @AluminiumTech's original question

 

if (URL == OnTask_AllowedWebsites[13])
            {
                IsOnTask = true;
            }

You never assign anything to [13] so you do have null variables.

That's not what fixed the issue though.........

 

I tried playing around and changed a few lines of code and I had no more issues. So idk what happened.

[AlTech]

7 minutes ago, Ryan_Vickers said:

hm, I suppose that's true if that really is the issue...

@AluminiumTech did he solve it?

IDK.

 

 

I changed something else and it worked.

 

I changed this and it worked.

     ontask.URL = text.Text;

                    CheckSecurity();

                    ///Check to see if it is allowed or not.
                    ontask.OnTask_TempNavigate();

                    if(ontask.IsOnTask == true)
                    {
                        TempNavigate();
                    }
                    else if(ontask.IsOnTask == false)
                    {
                        //Tell the user to stay on task if they attempt to navigate to a URL which is not allowed.
                        dialog.StayOnTask();
                    }

 

I also removed the unused value just now and I will report back on results.

 

14 minutes ago, Ryan_Vickers said:

 

oh no I knew this would happen... we've gone completely off topic  

Do any of you know how to solve the actual problem?

 

(I'm sorry I brought up the loop thing, I knew it was a bad idea  )

No no. i'd like suggestions on how to do it as a loop since the problem may have been fixed.

[madknight3]

13 minutes ago, squirrl said:

There is no Array.Contains method. (You're probably thinking of string.contains)

IndexOf would just be 

if  (OnTaskNotAllowedWebsites.IndexOf(URL) != -1) {
// URL matches one of the websites
}

 

You can use Contains on arrays as well. I tried it before posting to make sure.

string[] s = {"hello", "there"};
s.Contains("hello"); // returns true
s.Contains("he"); // returns false

Note this works for all primitive types, not just string.

[squirrl]

Just now, AluminiumTech said:

That's not what fixed the issue though.........

 

I tried playing around and changed a few lines of code and I had no more issues. So idk what happened.

 

Ah well, If the issue wasn't in the code that you posted then there's no way we would have found it then.

[AlTech]

1 minute ago, squirrl said:

Ah well, If the issue wasn't in the code that you posted then there's no way we would have found it then.

No no. It was in the code I posted.

 

It just wasn't what I expected it to be. But how can I make a more efficient process of checking against the URL?

 

[squirrl]

Just now, AluminiumTech said:

No no. It was in the code I posted.

 

It just wasn't what I expected it to be. But how can I make this a more efficient process of checking?

 

 

Look above. You can use array.indexOf or array.contains

[squirrl]

1 minute ago, AluminiumTech said:

No no. It was in the code I posted.

 

It just wasn't what I expected it to be. But how can I make this a more efficient process of checking?

 

 

The code you posted just then isn't in the OP.

[AlTech]

Just now, squirrl said:

The code you posted just then isn't in the OP.

Ohhhhhhhhhhhhhh. My bad .

 

It was part of the main section of the program.

 

1 minute ago, squirrl said:

Look above. You can use array.indexOf or array.contains

But wouldn't it mean it would use as many if statements as right now?

[vanished]

9 minutes ago, AluminiumTech said:

No no. i'd like suggestions on how to do it as a loop since the problem may have been fixed.

Oh good I'm glad this turned out well in the end  

[AlTech]

Just now, Ryan_Vickers said:

Oh good I'm glad this turned out well in the end  

What was your loop idea or whatever to make it more clean and less if statements?

[squirrl]

Just now, AluminiumTech said:

 

But wouldn't it mean it would use as many if statements as right now?

 

Nope, since you're checking if the whole array contains the URL rather than checking if the URL exists in each individual position in the array.

You will end up with 3 if statements using the same logic as you have now.

I do think the logic needs modifying, though. If a website isn't on either list, is it supposed to be on task or not? If it's not on task then you don't need the blacklist, if it's on task then you don't need the whitelist.

And like i mentioned, the whole blacklist becomes useless when you overwrite the onTask variable when you have an allowed extenstion like.com which also appears on sites in the blacklist.

[vanished]

1 minute ago, AluminiumTech said:

What was your loop idea or whatever to make it more clean and less if statements?

I would do something like this: (keep in mind I know nothing of C#)

 

for (int i = 0; i < 12; i++) {

if (URL == OnTask_AllowedWebsites[ i ]) {

IsOnTask = true;

}

}

 

I apologize for the formatting but it's currently taking every ounce of self control to not go off on a mad rant about the code editor

[AlTech]

2 minutes ago, squirrl said:

Nope, since you're checking if the whole array contains the URL rather than checking if the URL exists in each individual position in the array.

You will end up with 3 if statements using the same logic as you have now.

I do think the logic needs modifying, though. If a website isn't on either list, is it supposed to be on task or not? If it's not on task then you don't need the blacklist, if it's on task then you don't need the whitelist.

And like i mentioned, the whole blacklist becomes useless when you overwrite the onTask variable when you have an allowed extenstion like.com which also appears on sites in the blacklist.

So it would look something like this?

if(OnTask_AllowedExtension.Contains(URL))
   {
//Do something here
   }
else if(OnTask_NotAllowedWebsites.Contains(URL))
{
  //Do something here
}
else if(OnTask_AllowedWebsites.Contains(URL))
{
  //Do something here
}

 

[squirrl]

2 minutes ago, AluminiumTech said:

So it would look something like this?

 

 

 

 

Yeah, pretty much. Now that it's clearer i can see you're using elseif so forget what I said before about the variable getting overwritten. The order still matters though. I'm sure the way you have it there it will allow every website with a .com extension. Surely you will check allowed Websites first, then Not Allowed, then Extensions?  

[AlTech]

Just now, AluminiumTech said:

So it would look something like this?

if(OnTask_AllowedExtension.Contains(URL))
   {
//Do something here
   }
else if(OnTask_NotAllowedWebsites.Contains(URL))
{
  //Do something here
}
else if(OnTask_AllowedWebsites.Contains(URL))
{
  //Do something here
}

 

or actually I think I can simplify that further.

 

if(OnTask_AllowedExtension.Contains(URL) & OnTask_AllowedWebsites.Contains(URL))
   {
//Do something here
   }
else if(OnTask_NotAllowedWebsites.Contains(URL))
{
  //Do something here
}