Serialize a Bitmap in C#/.NET to XML

Question

I want to XML-Serialize a complex type (class), that has a property of type System.Drawing.Bitmap among others.

    /// <summary>
    /// Gets or sets the large icon, a 32x32 pixel image representing this face.
    /// </summary>
    /// <value>The large icon.</value>
    public Bitmap LargeIcon { get; set; }

I now have found out that serializing the Bitmap with the default XML serializer does not work, because it does not have a public parameterless constructor, which is mandatory with the default xml serializer.

I am aware of the following:

• There exists a workaround, posted here: http://www.dotnetspider.com/resources/4759-XML-Serialization-C-Part-II-Images.aspx . However since this includes adding another property this seems to me a bit of a hack.
• There is also a deep XML serializing project on sourceforge.

I rather would not like referencing another project nor extensively tweak my class to just allow xml serialization of those bitmaps.

Is there no way to keep that simple?

Many thanks, Marcel

Answer 1

The BitMap class has not been designed to be easily XML Serialized. So, no, there's not simple way to correct a design decision.

Answer 2

You can also to implement ISerializable and to use SerializationInfo to deal manually with your bitmap content.

EDIT: João is right: Correct way to deal with XML serialization is to implement IXmlSerializable, not ISerializable:

public class MyImage : IXmlSerializable
{
    public string Name  { get; set; }
    public Bitmap Image { get; set; }

    public System.Xml.Schema.XmlSchema GetSchema()
    {
        throw new NotImplementedException();
    }

    public void ReadXml(System.Xml.XmlReader reader)
    {
        throw new NotImplementedException();
    }

    public void WriteXml(System.Xml.XmlWriter writer)
    {
        writer.WriteStartElement("Name");
        writer.WriteString(this.Name);
        writer.WriteEndElement();

        using(MemoryStream ms = new MemoryStream())
        {
            this.Image.Save(ms, ImageFormat.Bmp );
            byte[] bitmapData = ms.ToArray();
            writer.WriteStartElement("Image");
            writer.WriteBase64(bitmapData, 0, bitmapData.Length);
            writer.WriteEndElement();
        }
    }
}

Answer 3

I would do something like:

[XmlIgnore]
public Bitmap LargeIcon { get; set; }

[Browsable(false),EditorBrowsable(EditorBrowsableState.Never)]
[XmlElement("LargeIcon")]
public byte[] LargeIconSerialized
{
    get { // serialize
        if (LargeIcon == null) return null;
        using (MemoryStream ms = new MemoryStream()) {
            LargeIcon.Save(ms, ImageFormat.Bmp);
            return ms.ToArray();
        }
    }
    set { // deserialize
        if (value == null) {
            LargeIcon = null;
        } else {
            using (MemoryStream ms = new MemoryStream(value)) {
                LargeIcon = new Bitmap(ms);
            }
        }
    }
}

Answer 4

Implement IXmlSerializable and then handle all the serialization details yourself.

Since you say it's a large type and you only have a problem with the bitmap consider doing something like this:

public class BitmapContainer : IXmlSerializable
{
    public BitmapContainer() { }

    public Bitmap Data { get; set; }

    public XmlSchema GetSchema()
    {
        throw new NotImplementedException();
    }

    public void ReadXml(XmlReader reader)
    {
        throw new NotImplementedException();
    }

    public void WriteXml(XmlWriter writer)
    {
        throw new NotImplementedException();
    }
}

public class TypeWithBitmap
{
    public BitmapContainer MyImage { get; set; }

    public string Name { get; set; }
}