Using array in if condition to know if the index is null in c#

Question

I have declared my array like this,

string[] timeArrivalArray = new string[10];

Now, let's assume that on every click on the add button, something is inserting there.

However I want to use an if condition to a certain index. I want to use something like this

if (timeArrivalArray[] == [2]) {
}

Now whenever I click the button, the timeArrivalArray[] will check if it's already in the 2nd index and then execute the code. tl;dr I just want to use the if condition to the 2nd index, how can this be?

EDIT:
My problem is it's throwing excemption in the first increment. I have a button and something inserting from some variables. However, the code above is inserted in this

if (timeArrivalArray[] == [2]) {
    //*insert variable this*
} else {
    // *insert variable that*
}

EDIT 2:
Yes it's not the correct syntax and I just know how to do it. But the root of my problem is this

 DateTime theCalcu = DateTime.ParseExact(timeArrivalArray[2], "h:mm tt", System.Globalization.CultureInfo.InvariantCulture);

It's throwing me String reference not set to an instance of a String. Maybe because he can't find any index to the preceding indexes. Any suggestion would do.

It's unclear what you are asking. Please add a code which shows what the button is supposed to do and reword the question and say what the problem is. — Reza Aghaei, Dec 02 '16 at 01:11
I don't understand this. Do you just want something like `if(timeArrivalArray[2]=="Whatever")`? — Jens, Dec 02 '16 at 01:11
Gentlemen, I've edited my question. Sorry for the question but I can't think straight anymore. — Fiendcoder1, Dec 02 '16 at 01:18
the `if` logic check does not look right to me. are you sure this is C# ? — t0mm13b, Dec 02 '16 at 01:19
Yes it's c#, that's just a metaphoric way of how I visualize what I want to do. But before going to index number 2. it's throwing excemption because he can't find any value for index number 0 and 1 — Fiendcoder1, Dec 02 '16 at 01:23
You have not studied C# enough to warrant the code that conforms to [MCVE]. `if (timeArrivalArray[] == [2])` is wrong. — t0mm13b, Dec 02 '16 at 01:24
Voting to close, as the question is very poor, no [MCVE], the code is not even C#. — t0mm13b, Dec 02 '16 at 01:27
That exception is coming because `timeArrivalArray[2]` is null. There is no surprise in there. — RBT, Dec 02 '16 at 01:40
Possible duplicate of [What is a NullReferenceException, and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Dour High Arch, Dec 02 '16 at 02:10

score 0 · Answer 1 · answered Dec 02 '16 at 01:24

0

As much as I could comprehend from your post here is the logic I can think of. You can let me know what doesn't work out of it.

string[] timeArrivalArray = new string[10];
public void Button1_Click(object sender, EventArgs e)
        {
            if (timeArrivalArray[2] == null)
            {
                //keep inserting into the array since 2nd index is null
            }
            else if (timeArrivalArray[2] != null && timeArrivalArray[2] == "someInputValue")
            {
                //2nd index is non null and some existing value found  
                //so do something else
            }
            else
            {
                //2nd index isn't null but input value wasn't found so keep inserting
            }
        }

answered Dec 02 '16 at 01:24

RBT

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checking for null is not really useful as the C#'s `new` would have all the array initialized to empty string. – t0mm13b Dec 02 '16 at 01:25
2

Nope @t0mm13b. They will be initialized to null. string is a reference type. – RBT Dec 02 '16 at 01:26
1

woop... my bad, still, would be better to use `String.IsNullOrEmpty` [MSDN](https://msdn.microsoft.com/en-us/library/system.string.isnullorempty.aspx) – t0mm13b Dec 02 '16 at 01:32
Yep! I agree to that. `string.IsNullOrEmpty` is a better option if empty string is an invalid input which OP won't want to store in his array. – RBT Dec 02 '16 at 01:36

score 0 · Answer 2 · answered Dec 02 '16 at 07:56

whenever I click the button. The timeArrivalArray[] will check if it's already in the 2nd index[...] I just want to use the if condition to the 2nd index

This sounds to me like you want to count up the index every time a click occurs. If so you should specify an index variable outside of the scope of the click event:

string[] timeArrivalArray = new string[10];

int index = 0;

public void Button1_Click(object sender, EventArgs e)
{   // make sure you are not running out of bounds    
    if(index < timeArrivalArray.Length)
    {    
        if(index == 2)
        {
            timeArrivalArray[index] = //*insert variable this*
        } 
        else 
        {
            // *insert variable that*
        }        
    }

    index ++; // walk to the next position    
}

Using array in if condition to know if the index is null in c#

2 Answers2