Converting Array To Dictionary

MadDashCoder

I am trying to convert an array to a dictionary but my code is throwing a null exception. Below is my code

    static void Main(string\[\] args)
    {  
        Product p1 = new Product();
        p1.ProductSkew = 99;
        p1.ProductName = "Accord";
        p1.Color = "Black";
        p1.Price = 35000;

        Product p2 = new Product();
        p2.ProductSkew = 46;
        p2.ProductName = "Corvette";
        p2.Color = "Black";
        p2.Price = 65000;

        Product p3 = new Product();
        p3.ProductSkew = 35;
        p3.ProductName = "Altima";
        p3.Color = "Black";
        p3.Price = 32000;
        
        Product\[\] products = new Product\[3\];

        products\[0\] = p1;
        products\[1\] = p2;
        products\[2\] = p3;

        Dictionary productlist = products.ToDictionary(p => p.ProductSkew, p => p);

        foreach (KeyValuePair item in productlist)
        {
            Product product = new Product();
            product = item.Value;

            Console.WriteLine(
            "\\nSkew: {0} \\n" + "Name: {1} \\n" +  "Color: {2} \\n" +  "Price: {3} \\n",
            product.ProductSkew, product.ProductName, product.Color, product.Price );                
        }
        Console.ReadLine();
    }
}

public class Product
{
    public int ProductSkew { get; set; }
    public string ProductName { get; set; }        
    public string Color { get; set; }
    public double Price { get; set; }

    public void AddProduct()
    { 
        Console.WriteLine("Enter Product Skew.");
        this.ProductSkew = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("Enter Product Name.");
        this.ProductName = Console.ReadLine();

        Console.WriteLine("Enter Product Color.");
        this.Color = Console.ReadLine();

        Console.WriteLine("Enter Product Price.");
        this.Price = Convert.ToDouble(Console.ReadLine());
    }
}

The syntax seems correct but when I step through the code inside of ToDictionay(), p.ProduckSkew is empty and I don't know why. Any help is greatly appreciated, thanks.

John Torjo

This is weird. Just copy-pasted your code. - VS 2013 - .net 4.5 - debug and release Works as expected. Best, John

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MadDashCoder

Hi, thanks for replying. I think I know what the problem is. In my actual code I set the size of the array to 10 but inserted data into only three of the elements. So my question is how do I test for null values when converting an array to a dictionary. Thanks for your help.

Matt T Heffron

The most obvious solution would be to use List<Product> instead of Product[], and then use Products.Add(...); to populate the collection.

    List<Product> products = new List<Product>;

    products.Add(p1);
    products.Add(p2);
    products.Add(p3);

"Fairy tales do not tell children the dragons exist. Children already know that dragons exist. Fairy tales tell children the dragons can be killed." - G.K. Chesterton

Mathi Mani

Just add a where clause in your code like this:

Dictionary<int, Product> productlist = products.Where(b => b != null).ToDictionary(p => p.ProductSkew, p => p);

This will ignore all the null products and convert the rest into dictionary.

Sascha Lefevre

MadDashCoder wrote:

Dictionary<int, Product> productlist

Maybe it's because it's just a code sample but here you don't actually make use of the dictionary as such because you don't use its keys - a list would suffice. If it actually has to be a dictionary then I'd suggest you don't name it productlist ;)

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

MadDashCoder

Thank you Mathi, your solution works great. Also I will keep everyone else's suggestions in mind as they are all very valuable, thank you all.

Richard Deeming

MadDashCoder wrote:

Product product = new Product(); product = item.Value;

There's no point creating a new Product if you're just going to throw it away on the next line. Just use:

Product product = item.Value;

MadDashCoder wrote:

ProductSkew

I think you meant to write ProductSku - a Stock Keeping Unit. "Skew"[^] has a totally different meaning. :)

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Luc Pattyn

The fixed size array is a nono, this is where you should use some kind of a collection, probablye the List<Product> Matt already suggested. But if you know beforehand you will need a Dictionary (not sure you do!) maybe you could stuff the fresh products in the dictionary right away? :) PS: your Product class deserves to have a constructor that takes the basic values as parameters... PS2: ... as well as a ToString() to return a formatted representation of itself.

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