asp.net webapi 序列化为xml 时实体属性增加<![CDATA[]]>防止特殊字符

     有时webapi在序列化xml时，可能需要给某些带有html或特殊字符（如 < > & /）的字段加上<![CDATA[]]> 已防止影响xml正常数据，如果使用.aspx视图那可直接在前台绑定字段时直接加入<![CDATA[]]>，webapi只有后台代码，那只能在后台做了，如下。

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Threading.Tasks;
using System.Web.Http;
using System.Xml;
using System.Xml.Serialization;

namespace MvcApplication1.Controllers
{
    public class TestController : ApiController
    {
        [HttpGet]
        [HttpPost]
        public HttpResponseMessage HouseTest(string city)
        {
            //手动构造数据，这里应该是调用构造数据。
            var info = new GetHouseCountInfo()
            {
                CityName = "北京",
                CountInfo = new List<CountInfo>()
                {
                    new CountInfo()
                    {
                        Data = "2016-08-30",
                        HouseDetail = "描述信息1111等。。。"
                    },
                    new CountInfo()
                    {
                        Data = "2016-08-30",
                        HouseDetail = "描述信息2222等。。。"
                    },
                    new CountInfo()
                    {
                        Data = "2016-08-30",
                        HouseDetail = "描述信息333等。。。"
                    }
                }
            };
            //序列化实体与赋值
            var model = new HouseCountRoot {GetHouseInfo = new GetHouseCountInfo()};
            model.GetHouseInfo.CountInfo = info.CountInfo;
            model.Result = "";
            model.Message = "";
            model.GetHouseInfo.CityName = info.CityName;

            return new HttpResponseMessage()
            {
                Content =
                    new ObjectContent<HouseCountRoot>(model, new CustomNamespaceXmlFormatter() {UseXmlSerializer = true},
                        new System.Net.Http.Headers.MediaTypeHeaderValue("application/xml") {CharSet = "utf-8"}),
                StatusCode = HttpStatusCode.OK
            };
        }
    }

    [XmlRoot("houses")]
    public class HouseCountRoot
    {
        [XmlElement("result")]
        public string Result { get; set; }

        [XmlElement("message")]
        public string Message { get; set; }

        [XmlElement("housecount")]
        public GetHouseCountInfo GetHouseInfo { get; set; }
    }

    public class GetHouseCountInfo
    {
        /// <summary>
        /// 城市名称
        /// </summary>
        [XmlElement("cityname")]
        public string CityName { get; set; }

        /// <summary>
        /// 房源数信息
        /// </summary>
        [XmlElement("countinfo")]
        public List<CountInfo> CountInfo { get; set; }
    }

    public class CountInfo
    {
        /// <summary>
        /// 日期
        /// </summary>
        [XmlElement("data")]
        public string Data { get; set; }

        /// <summary>
        /// 加<![CDATA[ ]]>数据字段
        /// </summary>
        [XmlIgnore] //方式1，这里属性设置忽略，把CDataContent设置为housedetail
        public string HouseDetail { get; set; }

        [XmlElement("housedetail")]
        public XmlNode[] CDataContent
        {
            get
            {
                return new XmlNode[]
                {
                    new XmlDocument().CreateCDataSection(HouseDetail)
                };
            }
            set
            {
                HouseDetail =
                    value[0].Value;
            }
        }

        //方式二，这里把CDataContent设置为housedetail
        //[XmlElement("housedetail")]
        //public XmlNode CDataContent
        //{
        //    get
        //    {
        //        // 这种方式这里代码比上面的要多运行一定次数。
        //        XmlNode node = new XmlDocument().CreateNode(XmlNodeType.CDATA, "", "");
        //        node.InnerText = HouseDetail;
        //        return node;
        //    }
        //    set
        //    {
        //        HouseDetail
        //            = value.Value;
        //    } //省略则CDataContent不会被序列化
        //}

        //以下属性省略。。。。
    }

    /// <summary>
    /// 去除xml命名空间的 序列化类
    /// </summary>
    public class CustomNamespaceXmlFormatter : XmlMediaTypeFormatter
    {
        public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content,
            TransportContext transportContext)
        {
            var xns = new XmlSerializerNamespaces();
            foreach (var attribute in type.GetCustomAttributes(true))
            {
                var xmlRootAttribute = attribute as XmlRootAttribute;
                if (xmlRootAttribute != null)
                {
                    xns.Add(string.Empty, xmlRootAttribute.Namespace);
                }
            }

            if (xns.Count == 0)
            {
                xns.Add(string.Empty, string.Empty);
            }

            var task = Task.Factory.StartNew(() =>
            {
                var serializer = new XmlSerializer(type);
                serializer.Serialize(writeStream, value, xns);
            });

            return task;
        }
    }
}

结果如下。

<?xml version="1.0"?>
<houses>
  <result />
  <message />
  <housecount>
    <cityname>北京</cityname>
    <countinfo>
      <data>2016-08-30</data>
      <housedetail><![CDATA[描述信息1111等。。。]]></housedetail>
    </countinfo>
    <countinfo>
      <data>2016-08-30</data>
      <housedetail><![CDATA[描述信息2222等。。。]]></housedetail>
    </countinfo>
    <countinfo>
      <data>2016-08-30</data>
      <housedetail><![CDATA[描述信息333等。。。]]></housedetail>
    </countinfo>
  </housecount>
</houses>