Question

I am writing some code against the Azure Table Storage REST API. The API uses OData, which is normally handled by the .net client. However, I am not using the client, so I need to figure out another way to generate/consume OData XML. I can use the Syndication classes to do the ATOM stuff, but not the OData/EDM <-> CLR mapping.

Is anyone aware of a OData/EDM <-> type mapper, and/or CLR object to OData entity converter?

Thanks,
Erick

Answer 1

Here’s some code that converts an XML element (from an OData feed) and converts it to an ExpandoObject.

private static object GetTypedEdmValue(string type, string value, bool isnull)
{
    if (isnull) return null;

    if (string.IsNullOrEmpty(type)) return value;

    switch (type)
    {
        case "Edm.String": return value;
        case "Edm.Byte": return Convert.ChangeType(value, typeof(byte));
        case "Edm.SByte": return Convert.ChangeType(value, typeof(sbyte));
        case "Edm.Int16": return Convert.ChangeType(value, typeof(short));
        case "Edm.Int32": return Convert.ChangeType(value, typeof(int));
        case "Edm.Int64": return Convert.ChangeType(value, typeof(long));
        case "Edm.Double": return Convert.ChangeType(value, typeof(double));
        case "Edm.Single": return Convert.ChangeType(value, typeof(float));
        case "Edm.Boolean": return Convert.ChangeType(value, typeof(bool));
        case "Edm.Decimal": return Convert.ChangeType(value, typeof(decimal));
        case "Edm.DateTime": return XmlConvert.ToDateTime(value, XmlDateTimeSerializationMode.RoundtripKind);
        case "Edm.Binary": return Convert.FromBase64String(value);
        case "Edm.Guid": return new Guid(value);

        default: throw new NotSupportedException("Not supported type " + type);
    }
}

private static ExpandoObject EntryToExpandoObject(XElement entry)
{
    XNamespace xmlnsm = "http://schemas.microsoft.com/ado/2007/08/dataservices/metadata",
                xmlns = "http://www.w3.org/2005/Atom";

    ExpandoObject entity = new ExpandoObject();
    var dic = (IDictionary<string, object>)entity;

    foreach (var property in entry.Element(xmlns + "content").Element(xmlnsm + "properties").Elements())
    {
        var name = property.Name.LocalName;
        var type = property.Attribute(xmlnsm + "type") != null ? property.Attribute(xmlnsm + "type").Value : "Edm.String";
        var isNull = property.Attribute(xmlnsm + "null") != null && string.Equals("true", property.Attribute(xmlnsm + "null").Value, StringComparison.OrdinalIgnoreCase);
        var value = property.Value;

        dic[name] = GetTypedEdmValue(type, value, isNull);
    }

    return entity;
}