Merge two arrays in a Key => Value

Question

I have two arrays with the same length and I need to use the first as a Key and the second as a Value.

My Key is an unique string and my Value is a double. I have 6 capybaras. Their names will be the key and their weight is the pound.

My current code:

        ViewBag.MeuBalaioDeCapivaras = new string[]
        {
            "Jerimúndia",
            "Genoveva",
            "Facibulana",
            "Carnavala",
            "Dentinhos Dourados",
            "Creusa"
        };

        ViewBag.PesoDeCadaCapivaraDoMeuBalaioDeCapivaras = new double[]
        {
            500.0,
            400.0,
            250.0,
            12.0,
            1589.0,
            87.3
        };

This is my Arrays and I was doing as a KeyValuePair:

var keyValuePair = new KeyValuePair<string, double>(ViewBag.NomeDaCapivara, ViewBag.PesoDeCadaCapivaraDoMeuBalaioDeCapivaras);

It compiles perfectly, but in the end it gives me an exception, when running:

=> An exception of type 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' occurred in System.Core.dll but was not handled in user code. Additional information: The best correspondence of the overloaded method.

How can I do what I need?

http://stackoverflow.com/questions/4038978/map-two-lists-into-a-dictionary-in-c-sharp — John Bustos, Jul 30 '14 at 18:46

score 12 · Accepted Answer · answered Jul 30 '14 at 18:44

LINQ has a little-known function to do just that - Zip. The function takes two collections and merges them into a single collection:

int[] numbers = { 1, 2, 3, 4 };
string[] words = { "one", "two", "three" };

var numbersAndWords = numbers.Zip(words, (number, word) => new KeyValuePair<string,int>(word, number);

score 1 · Answer 2 · edited May 23 '17 at 11:45

Your code compiles because ViewBag is dynamic, this means there is no compile time checking.

If you replaced

var keyValuePair = new KeyValuePair<string, double>(ViewBag.NomeDaCapivara, ViewBag.PesoDeCadaCapivaraDoMeuBalaioDeCapivaras);

If you put the arrays in directly, you would get the compile time error you are expecting: e.g.

var keyValuePair = new KeyValuePair<string, double>(
    new string[] { "Jerimúndia", "Genoveva", "Facibulana", "Carnavala", "Dentinhos Dourados", "Creusa" },
new double[] { 500.0, 400.0, 250.0, 12.0, 1589.0, 87.3 });

Gives:

Compilation error (line x1, col y1): The best overloaded method match for 'System.Collections.Generic.KeyValuePair<string,double>.KeyValuePair(string, double)' has some invalid arguments
Compilation error (line x2, col y2): Argument 1: cannot convert from 'string[]' to 'string'
Compilation error (line x3, col y3): Argument 2: cannot convert from 'double[]' to 'double'

The old school, explicit way to do this would be something like:

    var meuBalaioDeCapivaras = new string[]
    {
    "Jerimúndia", "Genoveva", "Facibulana", "Carnavala", "Dentinhos Dourados", "Creusa"
    };

    var pesoDeCadaCapivaraDoMeuBalaioDeCapivaras = new double[]
    {
    500.0, 400.0, 250.0, 12.0, 1589.0, 87.3
    };

    var list = new List<KeyValuePair<string, double>>();

    for (var i = 0; i < meuBalaioDeCapivaras.Length; i++)
    {
        list.Add(new KeyValuePair<string, double>(meuBalaioDeCapivaras[i], pesoDeCadaCapivaraDoMeuBalaioDeCapivaras[i]));
    }

As Felipe Oriani and Avner Shahar-Kashtan have stated, if you are using .NET 3.5 or above, you can use Linq

would this cause an issue if the lengths are not checked, since the expected types for the KeyValuePair are not nullable, or no? — Brett Weber, Jul 30 '14 at 19:24
@BrettWeber Yes, it would. You should also check the types coming out of the `ViewBag` as well. What if you called `.Remove()` and it turned out to be a repository, rather than a list? — BanksySan, Jul 30 '14 at 19:32
hrm.. Ok, that helped out! I used linq for my attempts at a similar behavior, but if this is faster than my implementation, I'll be able to avoid those pitfalls whenever I get around to updating it. Thanks! — Brett Weber, Jul 30 '14 at 20:12

Merge two arrays in a Key => Value

2 Answers2