WCF 契约相关.该如何解决

WCF 契约相关...

C# code

[DataContract(Name = "LinkItem_Contract", Namespace = "http://schemas.thatindigogirl.com/samples/2006/06")]    public class LinkItem    {        private long m_id;        private string m_title;        private string m_description;        private DateTime m_dateStart;        private DateTime m_dateEnd;        private string m_url;        [DataMember(Name = "Id_Contract", IsRequired = false, Order = 0)]        public long Id        {            get { return m_id; }            set { m_id = value; }        }        [DataMember(Name = "Title_Contract", IsRequired = true, Order = 1)]        public string Title        {            get { return m_title; }            set { m_title = value; }        }}///调用 LinkItem_Contract item = new LinkItem_Contract();            item.Id_Contract = int.Parse(this.txtId.Text);            item.Title_Contract = this.txtTitle.Text;