ADO.NET: XMLSerialization of extended DataTable

Before 1,5 year I worked on the project, where we move all communication logic from .NET Remoting to WCF. In the architecture of the project our common transportation object is derived from Data Table. Due to some business rules this class has some additional fields. In .NET Remoting serialization of that kind of object works perfectly, but in WCF these additional fields isn’t serialized. The problem is due to changes serialization mechanism. Instead of binary serialization in .NET Remoting, in WCF serialization is XML based. In trying to solve this issue I created a post in MSDN Forums. Despite of that I found out the solution. This article explain my solution and give the community more clear view how to do it, instead of looking my old post in MSDN.

Lets say that we have this class that derives Data Table:

public class WcfDataTable : DataTable

{

    private string _ServerName;

 

    public WcfDataTable()

        : base()

    { }

 

    public WcfDataTable(string tableName)

        : base(tableName)

    { }

 

    public string ServerName

    {

        get { return this._ServerName; }

        set { this._ServerName = value; }

    }

}

 

 

Lets serialize instance of this class using XMLSerializer:

As you can see I’m creating dummy WcfDataTable object, which I’m cloning using xml serialization and deserialization. The cloned object is not identical with the original object, because this additional field is not initialized with the original value (it’s null). The existing xml serialization doesn’t catch the new field in the class. To make possible this field for xml serialization we should override the existing xml serialization, but how to do it? The solution is really simple. You have to implement the interface IXmlSerializable with explicit override of all its methods.

public class WcfDataTable : DataTable, IXmlSerializable

{

    private string _ServerName;

 

    public WcfDataTable()

        : base()

    { }

 

    public WcfDataTable(string tableName)

        : base(tableName)

    { }

 

    public string ServerName

    {

        get { return this._ServerName; }

        set { this._ServerName = value; }

    }

 

    void IXmlSerializable.ReadXml(System.Xml.XmlReader reader)

    {

        base.ReadXmlSchema(reader);

 

        XmlSerializer xmlSerializer = new XmlSerializer(typeof(string));

        this._ServerName = xmlSerializer.Deserialize(reader) as string;

 

        base.ReadXml(reader);

    }

 

    void IXmlSerializable.WriteXml(System.Xml.XmlWriter writer)

    {

        base.WriteXmlSchema(writer);

 

        XmlSerializer xmlSerializer = new XmlSerializer(typeof(string));

        xmlSerializer.Serialize(writer, this._ServerName);

 

        base.WriteXml(writer, XmlWriteMode.DiffGram);

    }

}

 

To do this workaround we have to override WriteXml and ReadXml method explicitly. The methods ReadXmlSchema and WriteXmlSchema are used to read and write the schema of data table, then we can read or write our data. Hence we can write/read our new field and then to invoke basic logic for serialization or deserializtion. So we reach our goal:

 

After this workaround you can see that our new field is serialized and deserialized successfully.

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