CODEWITHSUNDEEP
c#
milk way
milk way

Reputation: 17

What is the use of [,]?

string[,] table;

Will this really create a table for the console application in C# or is there an alternative way of creating a real table other than putting individual characters?

Upvotes: 1

Views: 87

Answers (2)

Richard
Richard

Reputation: 109035

string[,] table;

Declares (as comments have noted) a two-dimensional array. Thus:

table = new string[2,2];
table[0, 0] = "Top left";
table[0, 1] = "Bottom left";
table[1, 0] = "Top right";
table[1, 1] = "Bottom right":

(Using the obvious orientation.)

Compare:

// Three dimensional:
var table3 = new string[2,2,2];

// Array of arrays
string[][] tt = new string[2][];
tt[0] = new string[2];
tt[1] = new string[3]; // Second row is longer!
tt[0][0] = "Top left";
tt[0][1] = "Top right";
tt[1][0] = "Bottom left";
tt[1][1] = "Bottom right";
tt[1][2] = "Bottom extra right";

These are also known as Jagged Arrays.

EDIT Fuller demonstration of the latter case (which are generally more useful), including two ways to enumeration.

  • Nested loops are easy to understand, but you always need to (implicitly) have those nested loops.

  • Flattening into a single dimensional structure which allows a lot more power (because there is generally a lot more support for single dimensional structures across BCL and other libraries)

Of course using SelectMany is a steeper learning curve and is overkill for this simple case:

using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    static void Main(string[] args) {
        Console.WriteLine("Array of arrays");
        string[][] tt = new string[2][];
        tt[0] = new string[2];
        tt[1] = new string[3]; // Second row is longer!
        tt[0][0] = "Top left";
        tt[0][1] = "Top right";
        tt[1][0] = "Bottom left";
        tt[1][1] = "Bottom right";
        tt[1][2] = "Bottom extra right";

        NestedLoops(tt);
        Flatten(tt);
    }

    private static void NestedLoops(string[][] tt) {
        Console.WriteLine("  Nested:");
        for (int outerIdx = 0; outerIdx < tt.Length; ++outerIdx) {
            var inner = tt[outerIdx];
            for (int innerIdx = 0; innerIdx < inner.Length; ++innerIdx) {
                Console.WriteLine("    [{0}, {1}] = " + inner[innerIdx], outerIdx, innerIdx);
            }
        }
    }

    private static void Flatten(IEnumerable<string[]> tt) {
        Console.WriteLine("  Falattened:");
        var values = tt.SelectMany((innerArray, outerIdx)
                                => innerArray.Select((string val, int innerIdx)
                                    => new { OuterIndex = outerIdx, InnerIndex = innerIdx, Value = val }));
        foreach (var val in values) {
            Console.WriteLine("    [{0}, {1}] = " + val.Value, val.OuterIndex, val.InnerIndex);
        }
    }

}

Upvotes: 6

Marcus Persson
Marcus Persson

Reputation: 66

As said above, that's a two-dimensional string array. You can see it as a table for sure.

There is also a two-dimensional jagged array which is an array with different lengths. And there is also bigger multi-dimensional arrays as well.

But for your "table", if you got values in the array, you can use for-loop to get the values out from it. In your case, you need a nested for-loop to get the values added in, for example, a list box.

Upvotes: 0

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