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Different field serialization technique in ntext SQL field while keeping backward compatibility

TL, DR: we've been serializing some data in some tables of our SQL DB. Unfortunately that serialization technique wastes a lot of space for markup characters. We've found a new, more efficient way: to keep backwards compatibility, is it safe to adopt the following logic? -> When the serialization occurs, it always occurs using the new, more efficient way. When deserialization occurs, we check whether the string uses the new serialization format or the old one --> we then deserialize with the appropriate method. Is this robust? Can this be used in production? Aren't there any subtle problems with this approach?
Greetings. I'm working on an application which interacts with a SQL database. To achieve a specific business requirement, we've been serializing some data in a special column of our DB tables, of type ntext. Basically, in each cell of this column, we serialize an array of "Attributo" object, so typeof(T) is Attributo[]:
The "Attributo" definition is like the following:
public class Attributo
{
public virtual String Nome { get; set; }
public virtual String Valore { get; set; }
public virtual String Tipologia { get; set; }
}
- Deserialization to read the actual values:
XMLUtilities.Deserialize<Attributo[]>(value));
Serialization to store the values in the column (for each row..):
XMLUtilities.Serialize(attributes.ToArray());
And this is the helper class, which makes use of the XmlSerializer object:
public static class XMLUtilities
{
public static T Deserialize<T>(String xmlString)
{
XmlSerializer serializer = new XmlSerializer(typeof(T));
using (TextReader reader = new StringReader(xmlString))
{
return (T) serializer.Deserialize(reader);
}
}
public static String Serialize<T>(T xmlObject)
{
MemoryStream stream = new MemoryStream();
XmlSerializer serializer = new XmlSerializer(typeof(T));
XmlSerializerNamespaces xmlnsEmpty = new XmlSerializerNamespaces();
xmlnsEmpty.Add("", "");
serializer.Serialize(stream, xmlObject, xmlnsEmpty);
stream.Seek(0, SeekOrigin.Begin);
using (StreamReader reader = new StreamReader(stream))
{
return reader.ReadToEnd();
}
}
}
Now, the problem with this technique is that it wastes a lot of space for markup characters. This is an example string which is stored on the db:
<?xml version="1.0"?>
<ArrayOfAttributo>
<Attributo>
<Nome>Leakage_test_Time_prg1_p1</Nome>
<Valore>4</Valore>
<Tipologia>Single</Tipologia>
</Attributo>
<Attributo>
<Nome>Leakage_air_Volume_p1</Nome>
<Valore>14</Valore>
<Tipologia>Single</Tipologia>
</Attributo>
</ArrayOfAttributo>
So, we've found a more concise way of serializing these Attributo[], which produces this kind of output:
<ArrayOfA xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<A>
<N>Leakage_test_Time_prg1_p1</N>
<V>4</V>
<T>Single</T>
</A>
<A>
<N>Leakage_air_Volume_p1</N>
<V>14</V>
<T>Single</T>
</A>
</ArrayOfA>
then, to preserve backwards compatibility, which is the core issue we have implemented the following logic:
During serialization:
we always serialize in the new, more concise fashion
During deserialization:
we check whether the string starts with:
<?xml version="1.0"?>
or not. If that is the case, this is an old entry so we deserialize it in the old way. Otherwise, we deserialize using the new format.
We achieved that by decorating "Attributo" this way:
[DataContract(Name = "A", Namespace= "")]
public class Attributo
{
[DataMember(Name = "N")]
public virtual String Nome { get; set; }
[DataMember(Name = "V")]
public virtual String Valore { get; set; }
[DataMember(Name = "T")]
public virtual String Tipologia { get; set; }
}
and by performing the following changes to our serialization/deserialization methods, which now, for the new serialization technique, rely on DataContractSerializer object:
public static T Deserialize<T>(String xmlString)
{
//let's see if it's an old-style entry...
if (xmlString.StartsWith("<?xml version=\"1.0\"?>\r\n<ArrayOfAttributo>"))
{
try
{
XmlSerializer serializer = new XmlSerializer(typeof(T));
using (TextReader reader = new StringReader(xmlString))
{
return (T)serializer.Deserialize(reader);
}
}
catch { }
}
//..then it must be a new-style one
DataContractSerializer ser = new DataContractSerializer(typeof(T));
using (Stream s = _streamFromString(xmlString))
{
return (T) ser.ReadObject(s);
}
}
public static String Serialize<T>(T xmlObject)
{
MemoryStream stream1 = new MemoryStream();
DataContractSerializer ser = new DataContractSerializer(typeof(T));
ser.WriteObject(stream1, xmlObject);
stream1.Position = 0;
StreamReader sr = new StreamReader(stream1);
string xmlString = sr.ReadToEnd();
return xmlString;
}
private static Stream _streamFromString(string s)
{
MemoryStream stream = new MemoryStream();
StreamWriter writer = new StreamWriter(stream);
writer.Write(s);
writer.Flush();
stream.Position = 0;
return stream;
}
Everything seems to be working with this approach but we want to assess every possible risk before proceeding any further. Is this safe to use in production?

One more thing to keep in mind, while deserializing the older entry :
deserialize old-entry in old-style
serialize the old-entry in new-style
save the new-style-serialized-old-entry, and delete the old-style-serialized-old-entry.
You're good to go.

XMLSerializer Deserialization - array element order

We are using XMLSerializer.Deserialize(XMLReader) on .Net 4.5 to deserialize XML into an Object Graph generated by xsd.exe.
I would like to know what the expected deserialization behavior is for an array which is annotated with the XMLElementAttribute - specifically with regard to ordering. For example:
For the following property:
[System.Xml.Serialization.XmlElementAttribute("GivenName")]
public string[] GivenName {
// get() and set() methods
}
And the following XML:
<root>
<GivenName>One</GivenName>
<GivenName>Two</GivenName>
<GivenName>Three</GivenName>
</root>
Will this always deserialize as ['One', 'Two', 'Three']
So that the array order always matches the XML order
Also is there any documentation I can reference that clearly states this.
Thanks
Rob

Yes Its deserialize same order. Check the code sample code and output:
[System.SerializableAttribute()]
public class SampleClass
{
[System.Xml.Serialization.XmlElementAttribute(Order = 10)]
public string Foo { get; set; }
[System.Xml.Serialization.XmlElementAttribute(Order = 5)]
public string Bar { get; set; }
[System.Xml.Serialization.XmlElementAttribute("GivenName", Order = 15)]
public string[] GivenNames { get; set; }
}
class Program
{
static void Main(string[] args)
{
string[] names = new string[3] { "One", "Two", "Three" };
SampleClass TestObj = new SampleClass { Bar = "dsdfsdf", Foo = "test", GivenNames = names };
XmlSerializer SerializerObj = new XmlSerializer(typeof(SampleClass));
// Create a new file stream to write the serialized object to a file
TextWriter WriteFileStream = new StreamWriter(#"C:\files\test.xml");
SerializerObj.Serialize(WriteFileStream, TestObj);
// Cleanup
WriteFileStream.Close();
// Create a new file stream for reading the XML file
FileStream ReadFileStream = new FileStream(#"C:\files\test.xml", FileMode.Open, FileAccess.Read, FileShare.Read);
// Load the object saved above by using the Deserialize function
SampleClass LoadedObj = (SampleClass)SerializerObj.Deserialize(ReadFileStream);
// Cleanup
ReadFileStream.Close();
}
}

You can find some awesome information about it on msdn which is provide by microsoft.
This is the "official" documentation
The serialization is linear so you will alway get the same order normally.

ObservableCollection<BitmapImage> DataSerialize not serializing

I have a class that stores a ObservableCollection of BitmapImage's and I need to store this information in IsolatedStorage. I am using DataContract to do this with other class's which works. I am thinking that not being able to set the BitmapImage as a DataMember is stopping it from working.
Error message is:
Type 'System.Windows.Media.ImageSource' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute.
Any help would be appreciated.
CODE - Save to IsolatedStorage
public static void AddOrUpdateUnsavedItems(string key, List<ProcessClass> unsavedItems)
{
var store = IsolatedStorageFile.GetUserStoreForApplication();
if (store.FileExists("unsaveditem"))
{
store.DeleteFile("unsaveditem");
}
using (var stream = new IsolatedStorageFileStream("unsaveditem", FileMode.OpenOrCreate, FileAccess.Write, store))
{
DataContractSerializer dcs = new DataContractSerializer(typeof(List<ProcessClass>));
dcs.WriteObject(stream, unsavedItems);
}
}
CODE - Class
[DataContract]
public class ProcessClass
{
ObservableCollection<BitmapImage> images = new ObservableCollection<BitmapImage>();
[DataMember]
public ObservableCollection<BitmapImage> Images
{
get { return images; }
set { images = value; }
}
[DataMember]
public string Notes { get; set; }
[DataMember]
public string ItemID { get; set; }
}

BitmapImage is simply not serializable using data contract and there is no way to change this by yourself.
The only way to persist a BitmapImage (it's an image) is to use BinaryWriter or WriteableBitmap. An image converter for tranforming BitmapImage to byte[] and vice-versa will help too.

Windows Phone 8 - Error while Serializing/Deserializing XML

I have a Class A and Class B that contains List of class A objects.
public class Item
{
public string X{ get; set; }
public string Y{ get; set; }
}
public class ItemCollection
{
List<Item> items = new List<Item>();
//Some methods
}
I can serialize it by:
IsolatedStorageFileStream ifs = new IsolatedStorageFileStream("myxml.xml", FileMode.Create, isfile);
DataContractSerializer ser = new DataContractSerializer(itemlist.items.GetType());
XmlWriter writer = XmlWriter.Create(ifs);
ser.WriteObject(writer, itemlist.items);
But while deserializing it, I get "... Root element is missing." error.
IsolatedStorageFileStream ifs = new IsolatedStorageFileStream("myxml.xml", FileMode.Open, isfile);
DataContractSerializer ser = new DataContractSerializer(itemlist.Items.GetType());
XmlReader reader=XmlReader.Create(ifs);
itemlist.items= (List<Item>)ser.ReadObject(reader);
Is there any other/better way of serializing/deserializing one class that contains list/collection of another class?

It looks to me like the problem is simply that you are wiping the file when you open it to deserialize, via FileMode.Create. So of course the root element is missing: it is empty. You probably have the FileMode.Create and FileMode.Open inverted between the serialize/deserialize. And then add a few using for good measure.
The serialize should use FileMode.Create, to truncate or create the file fresh for new data.
The deserialize should use FileMode.Open, to look at the existing data.

XML Object Deserialization to Interface

I have two classes SccmAction and TicketAction which both implement interface IDelivery. These classes will be transmitted on a processing queue from which I just want to pull the message and act upon the Deliver method.
It seems however that I cannot deserialize to an interface because when I attempt to do so a System.NotSupportedException is thrown. From what I have gathered the XMLSerializer requires a concrete type for serialization. Does this leave me having to create an abstract class which implements IDelivery and inheriting SccmAction and ArsAction from it? Have I missed something that?
Edit Further Clarification
I may have a design flaw but my purpose is to pull messages off of a queue containing these objects. My intention was to have all objects coming off of this queue implement the interface ensuring that the application processing the objects just operates on the Deliver method. Each objects implementation of Deliver would vary.
Code to Deserialize
using (SqlConnection connection =
new SqlConnection(ConnectionString))
{
SqlCommand command = new SqlCommand(ReceiveString, connection);
connection.Open();
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
byte[] sb = (byte[])reader["message_body"];
SccmAction sa = DeserializeObject<SccmAction>(sb);
IDelivery iD = DeserializeObject<IDelivery>(sb);
}
reader.Close();
}
public static T DeserializeObject<T>(byte[] ba)
{
XmlSerializer xs = new XmlSerializer(typeof(T));
MemoryStream memoryStream = new MemoryStream(ba);
XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.UTF8);
return (T)xs.Deserialize(memoryStream);
}
Classes and Interface
[Serializable]
public class SccmAction : IDelivery
{
public string MachineName { get; set; }
public string CollectionName { get; set; }
public string Action { get; set; }
public DateTime EntryDateTime { get; set; }
public SccmAction () { }
public void Deliver()
{
throw new NotImplementedException();
}
}
[Serializable]
public class ArsAction : IDelivery
{
public string MachineName { get; set; }
public string CustomerName { get; set; }
public ArsAction() { }
public void Deliver()
{
throw new NotImplementedException();
}
}
public interface IDelivery
{
void Deliver();
}

Simply put, you can't serialize an interface without any dirtiness. But why do you want to serialize your interface anyway, it doesn't hold any state. It only has a declaration for a method.
You might want to create a Serialize method inside your classes. So they can serialize themselves individually, they know which type they are.
Besides, how do you expect the XmlSerializer to Deserialize to an exact type without providing it? It can't simply pick what to Deserialize to....
You could however change this line
IDelivery iD = DeserializeObject<IDelivery>(sb);
to this
IDelivery iD = DeserializeObject<SccmAction>(sb);
If you dont know what type you are deserializing to initially (ArsAction or SccmAction), then you can do something like this.
public static IDelivery DeserializeFromString(string xml)
{
//replace this stream with whatever you are useing
StringReader strReader = new StringReader(xml);
XmlReader reader = new XmlTextReader(fs); //important to use XmlReader
reader.MoveToContent(); //move to root
String className = reader.Name.Trim(); //read the class name
//use the namespace IDelivery is located in
className = "IDeliveryNamespace." + className;
//get the type
Type classType = Type.GetType(className);
XmlSerializer serializer = new XmlSerializer(Type.GetType(className));
// Declare an object variable of the type to be deserialized.
IDelivery i;
// Use the Deserialize method to restore the object's state.
i = (IDelivery)Convert.ChangeType(serializer.Deserialize(reader),classType);
return i;
}
Of course this assumes that you your Serializable class Name is not changed. Meaning ArsAction class serializes to and as far as I can tell from what you posted that is the case.
This code is a little dirty, but it should give you a starting point.