How to check Int array(Key) in Dictionary using ContainsKey method?

Question

I have a Dictionary collection with integer array as a Key and Image as Value. I need to check whether if same key is already exists or not , before adding new int[].

I have tried below code, but the Dictionary.ContainsKey(int[]) method will always fails, even the same key is already exists.

Dictionary<int[], Image> temp = new Dictionary<int[], Image>();
int[] rowcol = new int[]{rowIndex,colIndex};
if (!temp.ContainsKey(rowcol))
{
    animatedImage = style.BackgroundImage;
    temp.Add(rowcol, animatedImage);
}

Please suggest me how to check the int[] key in Dictionary?

Thanks

You're passing difference instances of an array which happens to contain the same items, of course they'll not be seen as the same. `new[] { 1 } == new[] { 1 }` also returns false. — Rob, Apr 19 '17 at 05:39
See also https://stackoverflow.com/questions/263400/what-is-the-best-algorithm-for-an-overridden-system-object-gethashcode — Peter Duniho, Apr 19 '17 at 05:42

score 2 · Answer 1 · edited Apr 22 '17 at 12:18

2

Try the following code:

private void sample()
{
    int rowIndex = 0;
    int colIndex = 0;
    Dictionary<int[], Image> temp = new Dictionary<int[], Image>();
    int[] rowcol = new int[] { rowIndex, colIndex };


    if (!(temp.Where(k => k.Key == rowcol).Count() > 0))
    {
        animatedImage = style.BackgroundImage;
        temp.Add(rowcol, animatedImage);
    }
}

edited Apr 22 '17 at 12:18

Donald Duck

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answered Apr 19 '17 at 05:46

Thomas

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Wow. That will not work because you also compare references. Changing `k.Key == rowcol` to `k.Key.SequenceEqual(rowcol)` might work but you'll lost the advantages of a dictionary over a list. Btw: you iterate over the all values even if the first value matches your contraint. Using `Any()` instead of `Count()` will stop after the first occurance. – Sebastian Schumann Apr 19 '17 at 05:50

How to check Int array(Key) in Dictionary using ContainsKey method?

1 Answers1