public class Tag<T>
    {
        [XmlAttribute(AttributeName = "value")]
        public T Value { get; set; }

        public static implicit operator Tag<T>(T value)
        {
            return new Tag<T> { Value = value };
        }
    }

    [XmlRoot(ElementName = "document")]
    public class Document
    {
        [XmlElement(ElementName = "tag1")]
        public Tag<int> Tag1 { get; set; }
        [XmlElement(ElementName = "tag2")]
        public Tag<string> Tag2 { get; set; }
        [XmlElement(ElementName = "tag3")]
        public Tag<DateTime> Tag3 { get; set; }
        [XmlElement(ElementName = "tag4")]
        public Tag<int> Tag4 { get; set; }
        [XmlElement(ElementName = "tag5")]
        public Tag<DateTime> Tag5 { get; set; }
        [XmlElement(ElementName = "tag6")]
        public Tag<string> Tag6 { get; set; }
        [XmlElement(ElementName = "tag7")]
        public Tag<decimal> Tag7 { get; set; }
    }