Serializing a BitmapImage in WinRT

public static async Task SaveFileAsync(string FileName, T data)
{
    MemoryStream memStream = new MemoryStream();
    DataContractSerializer serializer = new DataContractSerializer(typeof(T));
    serializer.WriteObject(memStream, data);

    StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(FileName,
        CreationCollisionOption.ReplaceExisting);
    using (Stream stream = await file.OpenStreamForWriteAsync())
    {
        memStream.Seek(0, SeekOrigin.Begin);
        await memStream.CopyToAsync(stream);
        await stream.FlushAsync();
    }
}

public static async Task<T> RestoreFileAsync(string FileName)
{
    T result = default(T);
    try
    {
        StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync(FileName);
        using (IInputStream inStream = await file.OpenSequentialReadAsync())
        {
            DataContractSerializer serializer = new DataContractSerializer(typeof(T));
            result = (T)serializer.ReadObject(inStream.AsStreamForRead());
            return result;
        }
    }

    catch (FileNotFoundException)
    {
        return default(T);
    }
}

I'm using these methods to serialize my data, but i have a class that contains an image,

[DataMember]
Public Image img{get;set;}

I'm trying to serialize it. I'm doing the following actually

var thumb = await item.GetThumbnailAsync(Windows.Storage.FileProperties.ThumbnailMode.PicturesView,
                        1000, Windows.Storage.FileProperties.ThumbnailOptions.UseCurrentScale);

BitmapImage bmg = new BitmapImage();
bmg.SetSource(thumb);
Image img = new Image();
img.Source = bmg;

i tried to serialize the bitmapImage it self but it is the same problem. i keep getting this error, and my BitmapImage has an attribute.

Type 'Windows.UI.Xaml.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. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.

DataContractSerializer won't work with images. You should either use BitmapEncoder (if you are dealing with WriteableBitmap or simply serialize the source address of your BitmapImage. If the bitmap was loaded from a local path or a temporary URL and you want to persist the entire bitmap - you can't extract the bitmap bits from BitmapImage anyway and so you need to either download the source file from the original source URL or copy the local file you loaded. You could then either save that copy as a loose file or serialize as say Base64 inside of your DataContractSerializer-created XML.