Question

Consider the following overly simplified chunk of XML:

<ElementA>
   <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#integer">5
   </AttributeValue>
</ElementA>

Specifically, looking at the AttributeValue element, from the DataType attribute, I know that my value is of type integer (though it could have been a double, string, datetime…any established datatype from the w3 standard). I would like to deserialize this xml to a .NET class with the strongly typed value. The first thing that came to my mind is to create a generic AttributeValue class:

public class AttributeValue<T>
{
    public T Value {get; set;}
}

but of course this won’t work for a couple of reasons – the biggest one being I would have to declare the type in the parent class which won’t compile because T is not defined:

public class ElementA
{
    public AttributeValue<T> {get; set; }  // Naturally, this will not work because T
}                                          // is not defined.

Plus, I would likely have to implement IXmlSerializable on my class to handle the custom serialization.

Is there a better way to solve this problem? I know I can serialize the DataType attribute in my code and store the value as a string, then convert later, but it would be helpful to actually have the correct type in my business object for later processing

Thanks for any help!

Jason

Answer 1

I appreciate your answer @caesay and I did implement it, but I’m not sure I require that type of functionality (to be able to add multiple properties to the dictionary). While I do use dynamo in dire need in my code, I try to avoid it where possible.

Instead, I implemented the following structure to retain the generic type within my parent class:

public class AttributeValueElement : XACMLElement
{

    public AttributeValueElement()
        : base(XacmlSchema.Context)
    {

    }

    [XmlAttribute]
    public string DataType { get; set; }


    [XmlText]
    public string Value 
    { 
        get { return DataValue.GetValue().ToString(); }
        set
        {
            DataValue = AttributeValueFactory.Create(DataType, value);   
        }
    }

    public AttributeValue DataValue { get; set; }        
}


public abstract class AttributeValue
{
    public AttributeValue()
    {

    }
    public abstract object GetValue();
}

public class AttributeValue<T> : AttributeValue
{
    public T Value { get; set; }
    public override object GetValue()
    {
        return Value;
    }
}

And a corresponding factory class to create the attribute value:

public static AttributeValue Create(string xacmlDataType, string value)
    {

        AttributeValue _attributeValue = null;

        switch (xacmlDataType)
        {
            case "http://www.w3.org/2001/XMLSchema#string":
            case "http://www.w3.org/2001/XMLSchema#x500Name":
            case "http://www.w3.org/2001/XMLSchema#ipAddress":
            case "http://www.w3.org/2001/XMLSchema#dnsName":
            case "http://www.w3.org/2001/XMLSchema#xPathExpression":
                _attributeValue = new AttributeValue<string> { Value = value };
                break;
            case "http://www.w3.org/2001/XMLSchema#boolean":
                _attributeValue = new AttributeValue<bool> {Value = XmlConvert.ToBoolean(value) };
                break;
            case "http://www.w3.org/2001/XMLSchema#integer":
                _attributeValue = new AttributeValue<int> { Value = XmlConvert.ToInt32(value) };
                break;
            case "http://www.w3.org/2001/XMLSchema#double":
                _attributeValue = new AttributeValue<double> { Value = XmlConvert.ToDouble(value) };
                break;
            case "http://www.w3.org/2001/XMLSchema#time":
            case "http://www.w3.org/2001/XMLSchema#date":
            case "http://www.w3.org/2001/XMLSchema#dateTime":
                _attributeValue = new AttributeValue<DateTime> { Value = XmlConvert.ToDateTime(value, XmlDateTimeSerializationMode.Utc) };
                break;
            case "http://www.w3.org/2001/XMLSchema#anyURI":
                _attributeValue = new AttributeValue<Uri> { Value = new Uri(value) };
                break;
            case "http://www.w3.org/2001/XMLSchema#hexInteger":
                _attributeValue = new AttributeValue<byte[]> { Value = Encoding.ASCII.GetBytes(value) };
                break;          
            case "http://www.w3.org/2001/XMLSchema#dayTimeDuration":
            case "http://www.w3.org/2001/XMLSchema#yearMonthDuration":
                _attributeValue = new AttributeValue<TimeSpan> { Value = XmlConvert.ToTimeSpan(value) };
                break;                
            default:
                throw new NotImplementedException("Data type '" + xacmlDataType + "' is not a supported type.");
        }           

        return _attributeValue;
    }

I hate to answer my own question on stackoverflow, but sometimes it happens.

Thanks for the responses guys!