C# 在C语言中，我无法将XML反序列化为对象

我已经看过了与此类似的各种问题，但无法找到有效的解决方案

我正在使用Visual Studio 2015社区，构建一个WPF项目

我从后端API获取xml，并试图将其转换为C对象，但无法使其工作

这是xml

<response>
    <computer_setting id="1" hospital_name="foo" computer_type="bar" environment="staging" label_printer_name="labels" document_printer_name="docs"/>
</response>

这是我反序列化它的尝试

// Get ComputerSettings
String _Url = this.ApiUrl
   + "/api1/hospitals/foo/settings.xml"
   + "?access_token=" + Authentication.AccessToken;

XmlSerializer _Serializer = new XmlSerializer(typeof(ComputerSettingResponse));
ComputerSettingResponse _ComputerSettingResponse = new ComputerSettingResponse();
using (XmlTextReader _XmlReader = new XmlTextReader(_Url))
{
    _ComputerSettingResponse = (ComputerSettingResponse)_Serializer.Deserialize(_XmlReader);
    Debug.WriteLine(_ComputerSettingResponse.Settings.Environment);
}

但当它到达Debug.WriteLine时，会引发NullReference异常

{对象引用未设置为对象的实例。}

---

我已经检查过url是否正确返回了xml，因此它一定是一个构造糟糕的类，或者我没有正确地进行反序列化。

一旦XDocument与Linq匹配，我就停止了所有xml属性voodoo。此映射代码简单明了

public class ComputerSettingResponse
{
    internal ComputerSetting Settings { get; set; }
}

internal class ComputerSetting
{

    internal string Id { get; set; }

    internal string HospitalName { get; set; }

    internal string ComputerType { get; set; }

    internal string Environment { get; set; }

    internal string LabelPrinterName { get; set; }

    internal string DocumentPrinterName { get; set; }
}

            string xmlString = @"<response>
    <computer_setting id=""1"" hospital_name=""foo"" computer_type=""bar"" environment=""staging"" label_printer_name=""labels"" document_printer_name=""docs""/>
</response>          ";

        XDocument xDoc = XDocument.Parse(xmlString);

        //XNamespace ns = XNamespace.Get("http://schemas.microsoft.com/developer/msbuild/2003");
        string ns = string.Empty;


        List<ComputerSettingResponse> collection = new List<ComputerSettingResponse>
        (
            from list in xDoc.Descendants(ns + "response")
            from item1 in list.Elements(ns + "computer_setting")
            where item1 != null
            select new ComputerSettingResponse
            {
                //note that the cast is simpler to write than the null check in your code
                //http://msdn.microsoft.com/en-us/library/bb387049.aspx
                Settings = new ComputerSetting
                (
                ) 
                {
                    Id = (string)item1.Attribute("id") ?? string.Empty,
                    HospitalName = (string)item1.Attribute("hospital_name") ?? string.Empty,
                    ComputerType = (string)item1.Attribute("computer_type") ?? string.Empty,
                    Environment = (string)item1.Attribute("environment") ?? string.Empty,
                    LabelPrinterName = (string)item1.Attribute("label_printer_name") ?? string.Empty,
                    DocumentPrinterName = (string)item1.Attribute("document_printer_name") ?? string.Empty
                }
            }
        );

        /* if you know there is only one */
        ComputerSettingResponse returnItem = collection.FirstOrDefault();

---

在上面的代码中，您似乎将Url视为XML，但它只是后端API的Url，不是吗

我尝试用您的示例XML替换它，并仅通过将类可见性更改为public使其工作

这对我来说很有效：

        String xml = File.ReadAllText("XMLFile1.xml");
        XmlSerializer _Serializer = new XmlSerializer(typeof(ComputerSettingResponse));
        ComputerSettingResponse _ComputerSettingResponse = new ComputerSettingResponse();
        using (StringReader reader = new StringReader(xml))
        {
            _ComputerSettingResponse = (ComputerSettingResponse)_Serializer.Deserialize(reader);
            Debug.WriteLine(_ComputerSettingResponse.Settings.Environment);
        }

像这样使用类：

using System.Xml.Serialization;

namespace Casechek.Kiosk
{
    [XmlRoot("response")]
    public class ComputerSettingResponse
    {
        [XmlElement("computer_setting")]
        public ComputerSetting Settings { get; set; }
    }

    public class ComputerSetting
    {
        [XmlAttribute("id")]
        public string Id { get; set; }
        [XmlAttribute("hospital_name")]
        public string HospitalName { get; set; }
        [XmlAttribute("computer_type")]
        public string ComputerType { get; set; }
        [XmlAttribute("environment")]
        public string Environment { get; set; }
        [XmlAttribute("label_printer_name")]
        public string LabelPrinterName { get; set; }
        [XmlAttribute("document_printer_name")]
        public string DocumentPrinterName { get; set; }
    }
}

我研究了为什么它不能与内部声明一起工作，并找到了这样一个答案，它帮助我理解了XmlSerializer内部的一些事情：

---

希望这能有所帮助。

您的属性必须是公共的才能序列化。根据：

XML序列化是将对象的公共属性和字段转换为串行格式（在本例中为存储或传输XML）的过程

将设置从internal更改为public，它将正确反序列化您还必须将ComputerSetting上修改的类更改为public才能编译

---

顺便说一句，您不应该使用XmlTextReader，自从.NET2发布以来，一直不鼓励使用它。根据，您应该使用XmlReader.Create。

Visual Studio有一些很好的工具来从XML或JSON生成可序列化的类-只需将XML的示例复制到剪贴板，打开一个空类文件，并使用Visual Studio中的以下菜单路径将其粘贴为类：编辑->粘贴特殊->将XML粘贴为类…或者，在JSON的情况下，将JSON粘贴为类。

您可以简化所有属性获取程序-例如stringitem1.Attributeid？？string.Empty。item1永远不会为null。是的，我在url附近的评论中提到了这一点。但感谢您为OP提供了真实的示例代码。此解决方案允许您保留内部名称。需要考虑的事情。

using System.Xml.Serialization;

namespace Casechek.Kiosk
{
    [XmlRoot("response")]
    public class ComputerSettingResponse
    {
        [XmlElement("computer_setting")]
        public ComputerSetting Settings { get; set; }
    }

    public class ComputerSetting
    {
        [XmlAttribute("id")]
        public string Id { get; set; }
        [XmlAttribute("hospital_name")]
        public string HospitalName { get; set; }
        [XmlAttribute("computer_type")]
        public string ComputerType { get; set; }
        [XmlAttribute("environment")]
        public string Environment { get; set; }
        [XmlAttribute("label_printer_name")]
        public string LabelPrinterName { get; set; }
        [XmlAttribute("document_printer_name")]
        public string DocumentPrinterName { get; set; }
    }
}