A field initializer cannot reference the non-static field, method or property... help with code snippet

[ssclaire]

I came across this error in my code that I cannot fix: A field initializer cannot reference the non-static field, method, or property 'ConsoleApplication.Polygon.colorValues' So extracted what I thought was the relevant part of the code to post and ask for help. The problem is that now this simplified code works:confused:. But I cannot find the problem in the original, full-length code. Since the original code is too long to post here, I was hoping I could post the "working" code here with the error. Maybe someone could tell me at least what to look for. This is my working code. The code creates a class with two fields. Both fields are enumerations...

using System;

namespace ConsoleApplication
{
class Program
{
enum ColorType {Red, Green, Blue, Yellow}; // all possible colors
enum ShapeType {Square, Circle, Triangle}; // all possible shapes

    class Polygon
    {
        // each polygon has a color and a shape
        public ColorType Color { get; set; }
        public ShapeType Shape { get; set; }

        private Polygon() { }       // hide the default constructor
        public Polygon(ColorType color, ShapeType shape)
        {
            Color = color;
            Shape = shape;
        }
    }

The code then tries to create an array of these classes. The elements of the array contain each possible combination of the enumerations. To do that, I use Enum.GetValues() to get an array of possible enum values and use the Array.Length property to figure out the size of the array I will need to hold all the combinations.

    static void Main(string\[\] args)
    {
        Array colorValues = Enum.GetValues(typeof(ColorType));
        Array shapeValues = Enum.GetValues(typeof(ShapeType));
        Polygon\[\] allPolygons = new Polygon\[`colorValues`.Length \* `shapeValues`.Length\];

        int index = 0;
        foreach (ColorType color in colorValues)
        {
            foreach (ShapeType shape in shapeValues)
            {
                allPolygons\[index\] = new Polygon(color, shape);
                Console.WriteLine(allPolygons\[index\]);
                index++;
            }
        }
    }
}

}

I underlined the portion (above) that is generating the error: A field initializer cannot reference the non-static field, method, or pr

[S Senthil Kumar]

Your code works probably because you moved initialization of colorValues inside Main. Your original code probaly initialized them as part of the field declaration, like

class Program
{
Array colorValues = Enum.GetValues(typeof(ColorType));
Polygon[] allPolygons = new Polygon[colorValues.Length * shapeValues.Length];
}

That doesn't work - instance field initializers cannot refer to other instance field initializers. That means that you cannot refer to colorValues from any other instance field initializer. The typical solution is to move the initialization code to the constructor of the class.

Regards Senthil [MVP - Visual C#] _____________________________ My Blog | My Articles | My Flickr | WinMacro

[ssclaire]

Okay, I think it is the "cannot reference the non-static" part of the error which is relevant. If I move the Main() code into a class:

    class MyClass
    {
        Array colorValues = Enum.GetValues(typeof(ColorType));
        Array shapeValues = Enum.GetValues(typeof(ShapeType));
        Polygon\[\] allPolygons = new Polygon\[colorValues.Length \* shapeValues.Length\];

        public MyClass()
        {
            int index = 0;
            foreach (ColorType color in colorValues)
            {
                foreach (ShapeType shape in shapeValues)
                {
                    allPolygons\[index\] = new Polygon(color, shape);
                    Console.WriteLine(allPolygons\[index\]);
                    index++;
                }
            }
        }
    }

...and call it from Main()

    static void Main(string\[\] args)
    {
        MyClass myClass = new MyClass();
    }

I get the error. But how do I work around that? How would I create the private allPolygons array? What am I actually doing wrong?

[Christian Graus]

ssclaire wrote:

static void Main(string[] args) { Array colorValues = Enum.GetValues(typeof(ColorType)); Array shapeValues = Enum.GetValues(typeof(ShapeType)); Polygon[] allPolygons = new Polygon[colorValues.Length * shapeValues.Length];

If a method is static, it can't access a non static property as it has no instance to refer to.

Christian Graus Please read this if you don't understand the answer I've given you "also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )

[Christian Graus]

ssclaire wrote:

Array colorValues = Enum.GetValues(typeof(ColorType)); Array shapeValues = Enum.GetValues(typeof(ShapeType)); Polygon[] allPolygons = new Polygon[colorValues.Length * shapeValues.Length];

Seems to me like these should be static anyhow, they don't change between instances, right ?

Christian Graus Please read this if you don't understand the answer I've given you "also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )

[S Senthil Kumar]

Just move the code to the constructor and you'll be fine

class MyClass
{
Array colorValues = Enum.GetValues(typeof(ColorType));
Array shapeValues = Enum.GetValues(typeof(ShapeType));
Polygon[] allPolygons;

        public MyClass()
        {
           allPolygons =  = new Polygon\[colorValues.Length \* shapeValues.Length\];
        ...
        }

}

Regards Senthil [MVP - Visual C#] _____________________________ My Blog | My Articles | My Flickr | WinMacro

[ssclaire]

S. Senthil Kumar wrote:

The typical solution is to move the initialization code to the constructor of the class.

Cool. Moving the initialization of colorValues, shapeValues, and allPolygons to the constructor worked. Thanks. I think the full code design is "cleaner" when I declare the colorValues/shapeValues arrays as static (as mentioned below). Thank you everyone.