Serializing an array of integers using XmlSerializer

Question

I'm encountering a problem while trying to serialize a multi-dimensioned array of integers via XmlSerializer for an XNA project I'm working on. I'm able to serialize all of my other data (booleans, strings, even Colors, etc) without a hitch. I've also seen plenty of people claim that XmlSerializer will natively handle (single-dimensioned) arrays of integers as well. Is there a limitation regarding multi-dimensioned arrays, or is something else going on here?

Here's the relevant code:

int[,,] scoredata = scores;  // Populated with data elsewhere 

filename = Path.Combine(container.Path, "scoredata.sav"); 
stream = File.Open(filename, FileMode.Create); 
serializer = new XmlSerializer(typeof(int[,,])); 
serializer.Serialize(stream, scoredata);  // This line throws the exception. 
stream.Close(); 

The exception I receive is "An unhandled exception of type 'System.InvalidOperationException' occurred in System.Xml.dll. There was an error generating the XML document."

I've also tried using this array as a member variable in a struct (where all of my other player data is stored) but I get the same exception when doing things that way, as well, which leads me to believe that it's not a simple syntax error or anything like that.

Do I need to restructure my code to serialize via a single-dimensioned array, or is there something I'm overlooking?

Thanks in advance!

Answer 1

Read the inner-exceptions:

• There was an error reflecting type 'SomeType'. Cannot serialize member 'SomeType.Data' of type 'System.Int32[,,]', see inner exception for more details.
• Cannot serialize object of type System.Int32[,,]. Multidimensional arrays are not supported.

So no: multi-dimensional arrays simply aren't supported. You may have to shim it through as a single-dimension array... you can do this by having a separate property that does the translation:

[XmlIgnore]
public int[, ,] Data { get; set; }

[XmlElement("Data"), Browsable(false)]
[EditorBrowsable(EditorBrowsableState.Never)]
public int[] DataDto
{
    get { /* flatten from Data */ }
    set { /* expand into Data */ }
} 

Answer 2

It took me a while to figure out what should go into Marc's get and set braces to flatten and expand multi-dimensional arrays.

Here is my solution for 2D arrays.

In my case, I know at compile time that one of the dimensions is 4 so I did not have to store (somehow) the array dimensions.

    [XmlIgnore]
    public int[,] Readings { get; set; }
    [XmlArray("Readings")]
    public int[] ReadingsDto { 
        get { return Flatten(Readings); }
        set { Readings = Expand(value, 4); }
    }

    public static T[] Flatten<T>(T[,] arr)
    {
        int rows0 = arr.GetLength(0);
        int rows1 = arr.GetLength(1);
        T[] arrFlattened = new T[rows0 * rows1];
        for (int j = 0; j < rows1; j++)
        {
            for (int i = 0; i < rows0; i++)
            {
                var test = arr[i, j];
                arrFlattened[i + j * rows0] = arr[i, j];
            }
        }
        return arrFlattened;
    }
    public static T[,] Expand<T>(T[] arr, int rows0)
    {
        int length = arr.GetLength(0);
        int rows1 = length / rows0;
        T[,] arrExpanded = new T[rows0, rows1];
        for (int j = 0; j < rows1; j++)
        {
            for (int i = 0; i < rows0; i++)
            {
                arrExpanded[i, j] = arr[i + j * rows0];
            }
        }
        return arrExpanded;
    }