You could use this code (old API example) to save all the media.

protected static umbraco.DataLayer.ISqlHelper SqlHelper
{
    get { return umbraco.BusinessLogic.Application.SqlHelper; }
}

public static void SaveMedia()
{
    try
    {
        string sql = @"
        select un.id
        from umbracoNode un
        where un.nodeObjectType = @type";

        //Get all the media items.
        using (IRecordsReader dr = SqlHelper.ExecuteReader(sql, SqlHelper.CreateParameter("@type", Media._objectType)))
        {
            //Loop trough all the media items.
            while (dr.Read())
            {
                //Get the id of a media item.
                int mediaId = dr.GetInt("id");

                //Resave media
                Media media = new Media(mediaId);
                media.Save();
                media.XmlGenerate(new XmlDocument());
            }
        }
    }
    catch (Exception ex)
    {
    }
} 

Jeroen

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