NullReferenceException with an Array in C#

Question

I want to create an array containing all the Pushpin objects I am dealing with. While trying to populate the Array, I am getting a NullReferenceException Unhandled error thrown. I have read as much documentation as I can find and cannot work out what is going on.

I have tried at least the following:

Pushpin[] arrayPushpins;
int i = 0;
foreach (Result result in arrayResults)
                {
                    Pushpin pin;
                    pin = new Pushpin();
                    pin.Location = d;
                    myMap.Children.Add(pin);
                    arrayPushpins[i] = new Pushpin();
                    arrayPushpins.SetValue(pin, i);;
                    i++;
                }

AND...

Pushpin[] arrayPushpins;
int i = 0;
foreach (Result result in arrayResults)
                {
                    Pushpin pin;
                    pin = new Pushpin();
                    pin.Location = d;
                    myMap.Children.Add(pin);
                    arrayPushpins[i] = new Pushpin();
                    arrayPushpins[i] = pin;
                    i++;
                 }

And nothing seems to work... I get the NullReference error every time. Any ideas? Many thanks! Will.

Amittai Shapira · Accepted Answer · 2011-09-15 05:53:16Z

6

The problem is that you don't initialize your array:

Pushpin[] arrayPushpins = new Pushpin[10]; // Creates array with 10 items

You might consider using IEnumerable<Pushpin> if you don't know the number of items in advance, e.g:

IEnumerable<Pushpin> pushpins = new List<Pushpin>

edited Sep 15, 2011 at 5:53

answered Sep 15, 2011 at 5:42

Amittai Shapira

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2 Comments

Erik Philips Over a year ago

Why not use a IEnumerable Collection instead?

Will Gill Over a year ago

initialising the array fixed. Strange, I thought I had tried that too, but potentially not in combination with using the SetValue method. Thanks, Amittai. I will also try using a Collection, as I think you are all right - it will be better in this case as the number of pins can vary.

gn22 · Accepted Answer · 2011-09-15 05:44:01Z

1

You didn't initialize the array

 Pushpin[] arrayPushpins = new Pushpin[/*number goes here*/];
    int i = 0;
    foreach (Result result in arrayResults)
                    {
                        Pushpin pin;
                        pin = new Pushpin();
                        pin.Location = d;
                        myMap.Children.Add(pin);
                        arrayPushpins[i] = new Pushpin();
                        arrayPushpins.SetValue(pin, i);;
                        i++;
                    }

Edited to add: I'd avoid using a raw array, and go with something like a List<Pushpin> instead

answered Sep 15, 2011 at 5:44

gn22

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Comments

Neelesh · Accepted Answer · 2011-09-15 05:44:56Z

1

I think you should use a list instead of an array. That way, you won't have to know in advance how many elements will you have in your list.

answered Sep 15, 2011 at 5:44

Neelesh

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Comments

Mamta D · Accepted Answer · 2011-09-15 05:46:30Z

0

In your code, the array is only declared, not initialized. You need to initialize it with the new keyword.

Pushpin [] arrayPushpins= new Pushpin[50];

As the other answers recommend, you can use lists or collections.

answered Sep 15, 2011 at 5:46

Mamta D

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