Multi-dimensional foreach loop

Question

How can I properly do so that a check is performed for each string?

My code looks like :

string[,] screeny_baza = new string[300, 300];
for (int i = 0; i < 299; i++)
{
    try
    {
        string nazwa_screna_pokolei = screeny_baza[0,i]
    }
    catch { };
}

As i see i want to do just it one by one. Is it possible to do it faster omitting values that do not exist or have not been declared? They are just null i think.

I have dimension that looks like to 300/300 .

   X0 X1 X2
Y0 00 10 20
Y1 01 11 21
Y2 02 12 22

And want to save just string to each of dimesnion for example

string [00] = "bird";
string [01] = "bird2";

and later need to get this values in loop ( omitting values that do not exist or have not been declared)

Thanks for help.

Two dimensions will use a loop nested inside of another. And then of course you can check whether it is null before you act. — Broots Waymb
– Broots Waymb, Commented Oct 12, 2018 at 13:22
maybe there is better way to declare variables like it to faster get values? When i set only value for [150,150] it's gonna check every dimension , is it possible check only declared values? Here 150,150 — adam
– adam, Commented Oct 12, 2018 at 13:29
Do not worry about speed right now, seriously. For loops are fast. If you're experiencing noticeable slowdown, it's probably something else. Do not worry about premature optimization! — Broots Waymb
– Broots Waymb, Commented Oct 12, 2018 at 13:32
I don't if the question is "Foreach on 2d array", or through 2d array, or checking for null because of the try catch — Drag and Drop
– Drag and Drop, Commented Oct 12, 2018 at 13:37
See if you can work with jagged arrays instead. Then each row can have a foreach loop. — John Alexiou
– John Alexiou, Commented Oct 12, 2018 at 14:10

DaanV · Accepted Answer · 2018-10-12 13:31:26Z

2

I don't know about foreach loops on multi dimensional arrays but you can always do this:

string[,] screeny_baza = new string[300, 300];
for (int x = 0; x < screeny_baza.GetLength(0); x++)
{
    for (int y = 0; y < screeny_baza.GetLength(1); y++)
    {
        try
        {
            string nazwa_screna_pokolei = string.empty;
            if (screeny_baza[x, y] != null)
                nazwa_screna_pokolei = screeny_baza[x, y];
        }
        catch { };
    }
}

answered Oct 12, 2018 at 13:31

DaanV

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3 Comments

Drag and Drop Over a year ago

You can stackoverflow.com/questions/2834233/….

Fildor Over a year ago

@DragandDrop I don't seem to be able to make the connection. You can what ?

Drag and Drop Over a year ago

@ fildor he said "I dont know a bout for ach on multidim". Link is how to foreach. Missing a part of the comment with [foreach like this](link)

Drag and Drop · Accepted Answer · 2018-10-12 13:46:29Z

1

You can foreach on a 2d array. You can even LinQ Where to filter it.

var table = new string[20, 20];
table[0, 0] = "Foo";
table[0, 1] = "Bar";

foreach (var value in table.Cast<string>().Where(x =>!string.IsNullOrEmpty(x))) {
    Console.WriteLine(value);
}

answered Oct 12, 2018 at 13:46

Drag and Drop

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Comments

roozbeh S · Accepted Answer · 2018-10-12 15:11:05Z

Actually your try-catch block will not raise any exception because when you construct the array:

string[,] screeny_baza = new string[300, 300];

you can always index it as long as the indexes are in range; so the statement:

string nazwa_screna_pokolei = screeny_baza[0,i];

will execute without error. Just nazwa_screna_pokolei will be null;

Also if speed is concerned, a nested for-loop is much faster than LinQ. at least for this simple check. for example:

var list = screeny_baza.Cast<string>().Where(x => !string.IsNullOrEmpty(x)).ToList();

will take about 10 milliseconds, but

for (int i = 0; i < 300; i++)
{
    for (int j = 0; j < 300; j++)
    {
        if (string.IsNullOrEmpty(screeny_baza[i,j]))
        {
            continue;
        }
            list.Add(screeny_baza[i, j]);
    }
}

will take only 1 millisecond.

Cetin Basoz · Accepted Answer · 2018-10-12 13:33:39Z

For storing you would use row and column indices like:

screeny_baza[0,0] = "bird";
screeny_baza[0,1] = "bird";

For looping the values you use GetLength (though you know the dimensions as constant, this is a more flexible way):

for (int row = 0; row < screeny_baza.GetLength(0); row++) {
    for (int col = 0; col < screeny_baza.GetLength(1); col++) {
        if (!string.IsNullOrEmpty(screeny_baza[row,col])) // if there is a value
        Console.WriteLine($"Value at {row},{col} is {screeny_baza[row,col]}");
    }
}

Lev Yastrebov · Accepted Answer · 2019-10-12 15:47:03Z

My simple helper for such cases

    private static void forEachCell(int size, Action<int, int> action)
    {
        for (int i = 0; i < size; i++)
        {
            for (int j = 0; j < size; j++)
            {
                action(j, i);
            }
        }
    }

It can be modified to use different sizes. Usage example:

        double totalProbability = 0;

        forEachCell(chessboardSize, (row, col) =>
            totalProbability += boardSnapshots[movesAmount][row, col]);

        return totalProbability;

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