CODEWITHSUNDEEP
c#arraysgenericsdata-structures
Alexander Prokofyev
Alexander Prokofyev

Reputation: 34523

Is there a way to define a List<> of two elements string array?

I want to build two-dimentional array of strings where length of one dimention is 2. Similar to this

string[,] array = new string[,]
{
    {"a", "b"},
    {"c", "d"},
    {"e", "f"},
    {"g", "h"}
}

Doing

List<string[]> list = new List<string[]>();

list.Add(new string[2] {"a", "b"});
list.Add(new string[2] {"c", "d"});
list.Add(new string[2] {"e", "f"});
list.Add(new string[2] {"g", "h"});

list.ToArray();

gives me 

string[][]

but not 

string[,]

array.

Just curious, is there some trick to build dynamically

string[,]

array somehow?

Upvotes: 8

Views: 43249

Answers (6)

TheJoe
TheJoe

Reputation: 75

You could just use a struct. I do this when comparing XML Nodes manually.

private struct XmlPair
{
    public string Name { set; get; }
    public string Value { set; get; }
}

List<XmlPair> Pairs = new List<XmlPair>();

Upvotes: 1

hagensoft
hagensoft

Reputation: 1507

KeyValuePair did not work for me when I had to retrieve the values of the checkboxes on the controller as my model.Roles list was null. 

foreach (KeyValuePair<string, bool> Role in model.Roles){...}

The KeyValuePair structure doesn't have a default parameterless constructor and can't be instantiated by the model binder. I recommend a custom model class for your view that has just those properties. ASP.NET MVC 3 binding user control of type KeyValuePair to ViewModel

I found an implementation of a checkboxlist without the use of html helper at the following link CheckboxList in MVC3.0

Upvotes: 0

Terrence
Terrence

Reputation: 201

You can do this.

List<KeyValuePair<string, string>>

The idea being that the Key Value Pair would mimic the array of strings you replicated.

Upvotes: 20

Andrew Kennan
Andrew Kennan

Reputation: 14157

This isn't possible with a List<string[]>, as the type string[,] is different from string[].

Upvotes: 0

Robert Wagner
Robert Wagner

Reputation: 17793

The only way to do it would be to implement the ToArray() function yourself. You could implement it within your own collection (i.e. StringTupleCollection). This could work the same as ArrayList (i.e. internal array increasing in size as needed).

However I'm not sure the advantage of [x,2] over [x][2] (or even List<string[2]> would be significant enough to warrant the effort.

You could also write a StringTupple class as:

public class StringTupple : KeyValuePair<string, string>
{
}

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1503439

Well, you could reasonably easily write an extension method to do it. Something like this (only tested very slightly):

public static T[,] ToRectangularArray<T>(this IEnumerable<T[]> source)
{
    if (!source.Any())
    {
        return new T[0,0];
    }

    int width = source.First().Length;
    if (source.Any(array => array.Length != width))
    {
         throw new ArgumentException("All elements must have the same length");
    }

    T[,] ret = new T[source.Count(), width];
    int row = 0;
    foreach (T[] array in source)
    {
       for (int col=0; col < width; col++)
       {
           ret[row, col] = array[col];
       }
       row++;
    }
    return ret;
}

It's a slight shame that the above code uses T[] as the element type. Due to generic invariance I can't currently make source IEnumerable<IEnumerable<T>> which would be nice. An alternative might be to introduce a new type parameter with a constraint:

public static T[,] ToRectangularArray<T,U>(this IEnumerable<U> source)
    where U : IEnumerable<T>

Somewhat hairy, but it should work. (Obviously the implementation needs some changes too, but the basic principle is the same.)

Upvotes: 4

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