Asp.net mvc返回Xml结果，扩展Controller实现XmlResult以返回XML格式数据

我们都知道Asp.net MVC自带的Action可以有多种类型，比如ActionResult，ContentResult，JsonResult……，但是很遗憾没有支持直接返回XML的XmlResult。

当然，你也可以用ActionResult或者ContentResult，然后直接返回xml字符串。

如果我们想要想JsonResult一样来调用和返回xml结果，我们可以自己新建扩展XmlResult，该怎么办呢？不多说，看下面实例：

第一步，扩展System.Web.Mvc XmlRequestBehavior

/// <summary>
/// 扩展System.Web.Mvc XmlRequestBehavior
/// 指定是否允许来自客户端的HTTP GET请求
/// 熊仔其人/// </summary>
public enum XmlRequestBehavior
{
    /// <summary>
    /// HTTP GET requests from the client are allowed.
    /// 允许来自客户端的HTTP GET请求
    /// </summary>      
    AllowGet = 0,
    /// <summary>
    /// HTTP GET requests from the client are not allowed.
    /// 不允许来自客户端的HTTP GET请求
    /// </summary>
    DenyGet = 1,
}

第二步，实现XmlResult继承ActionResult

/// <summary>
/// 实现XmlResult继承ActionResult
/// 扩展MVC的ActionResult支持返回XML格式结果
/// 熊仔其人/// </summary>
public class XmlResult : ActionResult
{
    /// <summary>
    /// Initializes a new instance of the System.Web.Mvc.XmlResult class
    /// 初始化
    /// </summary>         
    public XmlResult() { }
    /// <summary>
    /// Encoding
    /// 编码格式
    /// </summary>
    public Encoding ContentEncoding { get; set; }
    /// <summary>
    /// Gets or sets the type of the content.
    /// 获取或设置返回内容的类型
    /// </summary>
    public string ContentType { get; set; }
    /// <summary>
    /// Gets or sets the data
    /// 获取或设置内容
    /// </summary>
    public object Data { get; set; }
    /// <summary>
    /// Gets or sets a value that indicates whether HTTP GET requests from the client
    /// 获取或设置一个值,指示是否HTTP GET请求从客户端
    /// </summary>
    public XmlRequestBehavior XmlRequestBehavior { get; set; }
    /// <summary>
    /// Enables processing of the result of an action method by a custom type that
    /// 处理结果
    /// </summary>
    /// <param name="context"></param>
    public override void ExecuteResult(ControllerContext context)
    {
        if (context == null) { throw new ArgumentNullException("context"); }
        HttpRequestBase request = context.HttpContext.Request;
        if (XmlRequestBehavior == XmlRequestBehavior.DenyGet && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidOperationException("XmlRequest_GetNotAllowed");
        }
        HttpResponseBase response = context.HttpContext.Response;
        response.ContentType = !string.IsNullOrEmpty(this.ContentType) ? this.ContentType : "application/xml";
        if (this.ContentEncoding != null)
        {
            response.ContentEncoding = this.ContentEncoding;
        }
        if (Data != null)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                XmlSerializer xs = new XmlSerializer(Data.GetType());
                xs.Serialize(ms, Data); // 把数据序列化到内存流中                     
                ms.Position = 0;
                using (StreamReader sr = new StreamReader(ms))
                {
                    context.HttpContext.Response.Output.Write(sr.ReadToEnd()); // 输出流对象 
                }
            }
        }
    }
}

注释：如果想要修改反序列化后的xml命名空间，可以使用自定义命名空间：

//使用你的定义的命名空间名称
var ns = new XmlSerializerNamespaces();
ns.Add("xsi", "http://api.xxxx.com/1.0/");

然后这里添加自定义命名空间，注意第三个参数
xs.Serialize(ms, Data ,ns); // 把数据序列化到内存流中 

第三步，扩展System.Mvc.Controller

/// <summary>
/// 扩展System.Mvc.Controller
/// 熊仔其人/// </summary>
public static class ControllerExtension
{
    public static XmlResult Xml(this Controller request, object obj) { return Xml(obj, null, null, XmlRequestBehavior.DenyGet); }
    public static XmlResult Xml(this Controller request, object obj, XmlRequestBehavior behavior) { return Xml(obj, null, null, behavior); }
    public static XmlResult Xml(this Controller request, object obj, Encoding contentEncoding, XmlRequestBehavior behavior) { return Xml(obj, null, contentEncoding, behavior); }
    public static XmlResult Xml(this Controller request, object obj, string contentType, Encoding contentEncoding, XmlRequestBehavior behavior) { return Xml(obj, contentType, contentEncoding, behavior); }

    internal static XmlResult Xml(object data, string contentType, Encoding contentEncoding, XmlRequestBehavior behavior) { return new XmlResult() { ContentEncoding = contentEncoding, ContentType = contentType, Data = data, XmlRequestBehavior = behavior }; }
}

到此就完成啦，下面就看看怎么调用：

第四步，在Controller里调用XmlResult

public ActionResult GetActionResult(string type)
{
    var data = new List<string>(); //注意，data必须是可被序列化的内容
    data.Add("A");
    data.Add("B");
    data.Add("C");

    if (type.ToLower() == "xml")
    {
        return this.Xml(data, XmlRequestBehavior.AllowGet);
    }
    else if (type.ToLower() == "json")
    {
        return Json(data, JsonRequestBehavior.AllowGet);
    }
    else {                  //error messages              
        return View("不支持此方法");
    }
}

public XmlResult GetXml()
{
    var data = new List<string>(); //注意，data必须是可被序列化的内容
    data.Add("A");
    data.Add("B");
    data.Add("C");
    return this.Xml(data, XmlRequestBehavior.AllowGet);
}

运行一下，看看实际返回结果吧！

上面的示例运行发挥的结果是这样：

<?xml version="1.0"?>
<ArrayOfString xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<string>A</string>
<string>B</string>
<string>C</string>
</ArrayOfString>

以下是完整的代码：

using System;
using System.IO;
using System.Text;
using System.Web;
using System.Web.Mvc;
using System.Xml.Serialization;

namespace Onexz.API.Models
{
    /// <summary>
    /// 扩展System.Web.Mvc XmlRequestBehavior
    /// 指定是否允许来自客户端的HTTP GET请求
    /// 熊仔其人/// </summary>
    public enum XmlRequestBehavior
    {
        /// <summary>
        /// HTTP GET requests from the client are allowed.
        /// 允许来自客户端的HTTP GET请求
        /// </summary>      
        AllowGet = 0,
        /// <summary>
        /// HTTP GET requests from the client are not allowed.
        /// 不允许来自客户端的HTTP GET请求
        /// </summary>
        DenyGet = 1,
    }

    /// <summary>
    /// 实现XmlResult继承ActionResult
    /// 扩展MVC的ActionResult支持返回XML格式结果
    /// 熊仔其人/// </summary>
    public class XmlResult : ActionResult
    {
        /// <summary>
        /// Initializes a new instance of the System.Web.Mvc.XmlResult class
        /// 初始化
        /// </summary>         
        public XmlResult() { }
        /// <summary>
        /// Encoding
        /// 编码格式
        /// </summary>
        public Encoding ContentEncoding { get; set; }
        /// <summary>
        /// Gets or sets the type of the content.
        /// 获取或设置返回内容的类型
        /// </summary>
        public string ContentType { get; set; }
        /// <summary>
        /// Gets or sets the data
        /// 获取或设置内容
        /// </summary>
        public object Data { get; set; }
        /// <summary>
        /// Gets or sets a value that indicates whether HTTP GET requests from the client
        /// 获取或设置一个值,指示是否HTTP GET请求从客户端
        /// </summary>
        public XmlRequestBehavior XmlRequestBehavior { get; set; }
        /// <summary>
        /// Enables processing of the result of an action method by a custom type that
        /// 处理结果
        /// </summary>
        /// <param name="context"></param>
        public override void ExecuteResult(ControllerContext context)
        {
            if (context == null) { throw new ArgumentNullException("context"); }
            HttpRequestBase request = context.HttpContext.Request;
            if (XmlRequestBehavior == XmlRequestBehavior.DenyGet && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
            {
                throw new InvalidOperationException("XmlRequest_GetNotAllowed");
            }
            HttpResponseBase response = context.HttpContext.Response;
            response.ContentType = !string.IsNullOrEmpty(this.ContentType) ? this.ContentType : "application/xml";
            if (this.ContentEncoding != null)
            {
                response.ContentEncoding = this.ContentEncoding;
            }
            if (Data != null)
            {
                using (MemoryStream ms = new MemoryStream())
                {
                    XmlSerializer xs = new XmlSerializer(Data.GetType());
                    xs.Serialize(ms, Data); // 把数据序列化到内存流中                     
                    ms.Position = 0;
                    using (StreamReader sr = new StreamReader(ms))
                    {
                        context.HttpContext.Response.Output.Write(sr.ReadToEnd()); // 输出流对象 
                    }
                }
            }
        }
    }

    /// <summary>
    /// 扩展System.Mvc.Controller
    /// 熊仔其人/// </summary>
    public static class ControllerExtension
    {
        public static XmlResult Xml(this Controller request, object obj) { return Xml(obj, null, null, XmlRequestBehavior.DenyGet); }
        public static XmlResult Xml(this Controller request, object obj, XmlRequestBehavior behavior) { return Xml(obj, null, null, behavior); }
        public static XmlResult Xml(this Controller request, object obj, Encoding contentEncoding, XmlRequestBehavior behavior) { return Xml(obj, null, contentEncoding, behavior); }
        public static XmlResult Xml(this Controller request, object obj, string contentType, Encoding contentEncoding, XmlRequestBehavior behavior) { return Xml(obj, contentType, contentEncoding, behavior); }

        internal static XmlResult Xml(object data, string contentType, Encoding contentEncoding, XmlRequestBehavior behavior) { return new XmlResult() { ContentEncoding = contentEncoding, ContentType = contentType, Data = data, XmlRequestBehavior = behavior }; }
    }

}

其他

常见的各种Result都是 ActionResult 派生的，都去各自实现 自己的 成员 及 核心过程： ExecuteResult
比如以下是JsonResult的部分源代码，我们可以看到它在核心 函数 ExecuteResult 做了头部处理，做了Http Body 内容处理：

public override void ExecuteResult(ControllerContext context)
{
  if (context == null)
    throw new ArgumentNullException("context");
  if (this.JsonRequestBehavior == JsonRequestBehavior.DenyGet && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
    throw new InvalidOperationException(MvcResources.JsonRequest_GetNotAllowed);
  HttpResponseBase response = context.HttpContext.Response;
  response.ContentType = string.IsNullOrEmpty(this.ContentType) ? "application/json" : this.ContentType;
  if (this.ContentEncoding != null)
    response.ContentEncoding = this.ContentEncoding;
  if (this.Data == null)
    return;
  JavaScriptSerializer scriptSerializer = new JavaScriptSerializer();
  if (this.MaxJsonLength.HasValue)
    scriptSerializer.MaxJsonLength = this.MaxJsonLength.Value;
  if (this.RecursionLimit.HasValue)
    scriptSerializer.RecursionLimit = this.RecursionLimit.Value;
  response.Write(scriptSerializer.Serialize(this.Data));
}

所以以此类推，如果你想做其他result，只需要根据result最终的样子  —— 核心通过派生ActionResult，并重写ExecuteResult 即可实现。

public class ImageResult : ActionResult
{
    public ImageResult() { }
    public Image Image { get; set; }
    public ImageFormat ImageFormat { get; set; }
    public override void ExecuteResult(ControllerContext context)
    {
        // verify properties 
        if (Image == null)
        {
            throw new ArgumentNullException("Image");
        }
        if (ImageFormat == null)
        {
            throw new ArgumentNullException("ImageFormat");
        }
        // output 
        context.HttpContext.Response.Clear();
        if (ImageFormat.Equals(ImageFormat.Bmp)) context.HttpContext.Response.ContentType = "image/bmp";
        if (ImageFormat.Equals(ImageFormat.Gif)) context.HttpContext.Response.ContentType = "image/gif";
        if (ImageFormat.Equals(ImageFormat.Icon)) context.HttpContext.Response.ContentType = "image/vnd.microsoft.icon";
        if (ImageFormat.Equals(ImageFormat.Jpeg)) context.HttpContext.Response.ContentType = "image/jpeg";
        if (ImageFormat.Equals(ImageFormat.Png)) context.HttpContext.Response.ContentType = "image/png";
        if (ImageFormat.Equals(ImageFormat.Tiff)) context.HttpContext.Response.ContentType = "image/tiff";
        if (ImageFormat.Equals(ImageFormat.Wmf)) context.HttpContext.Response.ContentType = "image/wmf";
        Image.Save(context.HttpContext.Response.OutputStream, ImageFormat);
    }
}

【完】