C# 反序列化返回空对象答案

【问题标题】：C# deserializer returns null objectC# 反序列化返回空对象
【发布时间】：2020-03-28 22:54:41
【问题描述】：

我尝试反序列化 xml，但它返回 null 对象。谷歌搜索，我发现它可能是根元素或注释的问题，所以我尝试更改它（XmlType，XmlRoot（ElementName =“...”）但没有效果。我在 stackoverflow 上阅读了几篇文章，但仍然没有找到解决方案。

我的 Xml 是：

<?xml version="1.0" encoding="UTF-8"?>
<VerificationResult>
  <Result code="0">TestResult</Result>
  <Description code="0000">TestDescription</Description>
  <SignatureID>TestSignatureID</SignatureID>
  <SigningTime>2019-02-02T14:16:13.186+01:00</SigningTime>
  <VerificationTime>2019-02-24T20:48:12Z</VerificationTime>
  <SigningCertificate certificateType="testcerttype">
    <Subject>CN=TestCN,OU=TestOU,O=TestO,C=TestC</Subject>
    <Issuer>CN=Digital Identification CA</Issuer>
    <Serial>45371416337571480875599671644328045627</Serial>
    <ValidFrom>2018-08-30T10:48:02Z</ValidFrom>
    <ValidTo>2021-08-29T10:48:02Z</ValidTo>
    <Base64Binary>
      base64binaryString
    </Base64Binary>
  </SigningCertificate>
  <RevocationInfo>
    <CRL>
      <Issuer>TestIssuer</Issuer>
      <CRLSerialNumber>9999999</CRLSerialNumber>
      <CRLThisUpdate>2019-03-24T10:40:51Z</CRLThisUpdate>
    </CRL>
  </RevocationInfo>
</VerificationResult>

和类：

[XmlRoot("VerificationResult")]
public class VerResult
{
    [XmlType("Result")]
    public class Result
    {
        [XmlAttribute(AttributeName = "code")]
        public string Code { get; set; }

        [XmlText]
        public string Text { get; set; }
    }

    [XmlType("Description")]
    public class Description
    {
        [XmlAttribute(AttributeName = "code")]
        public string Code { get; set; }

        [XmlText]
        public string Text { get; set; }
    }

    [XmlType("SigningCertificate")]
    public class SigningCertificate
    {
        [XmlElement(ElementName = "Subject")]
        public string Subject { get; set; }

        [XmlElement(ElementName = "Issuer")]
        public string Issuer { get; set; }

        [XmlElement(ElementName = "Serial")]
        public string Serial { get; set; }

        [XmlElement(ElementName = "ValidFrom")]
        public string ValidFrom { get; set; }

        [XmlElement(ElementName = "ValidTo")]
        public string ValidTo { get; set; }

        [XmlElement(ElementName = "Base64Binary")]
        public string Base64Binary { get; set; }

        [XmlAttribute(AttributeName = "certificateType")]
        public string CertificateType { get; set; }
    }

    [XmlType("CRL")]
    public class CRL
    {
        [XmlElement(ElementName = "Issuer")]
        public string Issuer { get; set; }

        [XmlElement(ElementName = "CRLSerialNumber")]
        public string CRLSerialNumber { get; set; }

        [XmlElement(ElementName = "CRLThisUpdate")]
        public string CRLThisUpdate { get; set; }
    }

    [XmlType("RevocationInfo")]
    public class RevocationInfo
    {
        [XmlElement(ElementName = "CRL")]
        public CRL CRL { get; set; }
    }

    [XmlType("VerificationResult")]
    public class VerificationResult
    {
        [XmlElement(ElementName = "Result")]
        public Result Result { get; set; }

        [XmlElement(ElementName = "Description")]
        public Description Description { get; set; }

        [XmlElement(ElementName = "SignatureID")]
        public string SignatureID { get; set; }

        [XmlElement(ElementName = "SigningTime")]
        public string SigningTime { get; set; }

        [XmlElement(ElementName = "VerificationTime")]
        public string VerificationTime { get; set; }

        [XmlElement(ElementName = "SigningCertificate")]
        public SigningCertificate SigningCertificate { get; set; }

        [XmlElement(ElementName = "RevocationInfo")]
        public RevocationInfo RevocationInfo { get; set; }
    }
}

下面的反序列化器返回空对象。

 public T Deserialize<T>(string input) where T : class
 {
     System.Xml.Serialization.XmlSerializer ser = new System.Xml.Serialization.XmlSerializer(typeof(T));

      using (StringReader sr = new StringReader(input))
      {
          return (T)ser.Deserialize(sr);
      }
  }

【问题讨论】：

哪一部分是空的？从反序列化返回？还是……？
var s = 反序列化(xml);返回空对象。
不，它没有；我在发布答案之前进行了测试。它返回一个没有成员的非空实例；在我的回答中，我添加了成员。我不认为 xmlserializer ever 为根对象返回 null （除非使用 xsi:nil，也许？）。你有一个实际的最小复制吗？因为那不是我运行代码时发生的事情

标签： c# xml

【解决方案1】：

您可以使用 Visual Studio 的 特殊粘贴 功能（编辑 -> 选择性粘贴 -> 将 XML 粘贴为类从您的 XML 生成相应的类。（当然还有其他方法，例如使用您可能不想（也不应该）使用的 dynamic）。

但是，如果这样做，我会得到以下类，它们可以与您的 XML 一起正常工作，因此您可能会在某处遇到一些命名或结构问题。（当然你可以优化生成的类，比如去掉所有的字段，但我希望这会有所帮助）：

// NOTE: Generated code may require at least .NET Framework 4.5 or .NET Core/Standard 2.0.
/// <remarks/>
[Serializable()]
[DesignerCategory("code")]
[XmlType(AnonymousType = true)]
[XmlRoot(Namespace = "", IsNullable = false)]
public partial class VerificationResult
{
    private VerificationResultResult resultField;
    private VerificationResultDescription descriptionField;
    private string signatureIDField;
    private DateTime signingTimeField;
    private DateTime verificationTimeField;
    private VerificationResultSigningCertificate signingCertificateField;
    private VerificationResultRevocationInfo revocationInfoField;

    /// <remarks/>
    public VerificationResultResult Result
    {
        get
        {
            return this.resultField;
        }
        set
        {
            this.resultField = value;
        }
    }

    /// <remarks/>
    public VerificationResultDescription Description
    {
        get
        {
            return this.descriptionField;
        }
        set
        {
            this.descriptionField = value;
        }
    }

    /// <remarks/>
    public string SignatureID
    {
        get
        {
            return this.signatureIDField;
        }
        set
        {
            this.signatureIDField = value;
        }
    }

    /// <remarks/>
    public DateTime SigningTime
    {
        get
        {
            return this.signingTimeField;
        }
        set
        {
            this.signingTimeField = value;
        }
    }

    /// <remarks/>
    public DateTime VerificationTime
    {
        get
        {
            return this.verificationTimeField;
        }
        set
        {
            this.verificationTimeField = value;
        }
    }

    /// <remarks/>
    public VerificationResultSigningCertificate SigningCertificate
    {
        get
        {
            return this.signingCertificateField;
        }
        set
        {
            this.signingCertificateField = value;
        }
    }

    /// <remarks/>
    public VerificationResultRevocationInfo RevocationInfo
    {
        get
        {
            return this.revocationInfoField;
        }
        set
        {
            this.revocationInfoField = value;
        }
    }
}

/// <remarks/>
[Serializable()]
[DesignerCategory("code")]
[XmlType(AnonymousType = true)]
public partial class VerificationResultResult
{
    private byte codeField;
    private string valueField;

    /// <remarks/>
    [XmlAttribute()]
    public byte code
    {
        get
        {
            return this.codeField;
        }
        set
        {
            this.codeField = value;
        }
    }

    /// <remarks/>
    [XmlText()]
    public string Value
    {
        get
        {
            return this.valueField;
        }
        set
        {
            this.valueField = value;
        }
    }
}

/// <remarks/>
[Serializable()]
[DesignerCategory("code")]
[XmlType(AnonymousType = true)]
public partial class VerificationResultDescription
{
    private byte codeField;
    private string valueField;

    /// <remarks/>
    [XmlAttribute()]
    public byte code
    {
        get
        {
            return this.codeField;
        }
        set
        {
            this.codeField = value;
        }
    }

    /// <remarks/>
    [XmlText()]
    public string Value
    {
        get
        {
            return this.valueField;
        }
        set
        {
            this.valueField = value;
        }
    }
}

/// <remarks/>
[Serializable()]
[DesignerCategory("code")]
[XmlType(AnonymousType = true)]
public partial class VerificationResultSigningCertificate
{
    private string subjectField;
    private string issuerField;
    private string serialField;
    private DateTime validFromField;
    private DateTime validToField;
    private string base64BinaryField;
    private string certificateTypeField;

    /// <remarks/>
    public string Subject
    {
        get
        {
            return this.subjectField;
        }
        set
        {
            this.subjectField = value;
        }
    }

    /// <remarks/>
    public string Issuer
    {
        get
        {
            return this.issuerField;
        }
        set
        {
            this.issuerField = value;
        }
    }

    /// <remarks/>
    [XmlElement(DataType = "integer")]
    public string Serial
    {
        get
        {
            return this.serialField;
        }
        set
        {
            this.serialField = value;
        }
    }

    /// <remarks/>
    public DateTime ValidFrom
    {
        get
        {
            return this.validFromField;
        }
        set
        {
            this.validFromField = value;
        }
    }

    /// <remarks/>
    public DateTime ValidTo
    {
        get
        {
            return this.validToField;
        }
        set
        {
            this.validToField = value;
        }
    }

    /// <remarks/>
    public string Base64Binary
    {
        get
        {
            return this.base64BinaryField;
        }
        set
        {
            this.base64BinaryField = value;
        }
    }

    /// <remarks/>
    [XmlAttribute()]
    public string certificateType
    {
        get
        {
            return this.certificateTypeField;
        }
        set
        {
            this.certificateTypeField = value;
        }
    }
}

/// <remarks/>
[Serializable()]
[DesignerCategory("code")]
[XmlType(AnonymousType = true)]
public partial class VerificationResultRevocationInfo
{
    private VerificationResultRevocationInfoCRL cRLField;

    /// <remarks/>
    public VerificationResultRevocationInfoCRL CRL
    {
        get
        {
            return this.cRLField;
        }
        set
        {
            this.cRLField = value;
        }
    }
}

/// <remarks/>
[Serializable()]
[DesignerCategory("code")]
[XmlType(AnonymousType = true)]
public partial class VerificationResultRevocationInfoCRL
{
    private string issuerField;
    private uint cRLSerialNumberField;
    private DateTime cRLThisUpdateField;

    /// <remarks/>
    public string Issuer
    {
        get
        {
            return this.issuerField;
        }
        set
        {
            this.issuerField = value;
        }
    }

    /// <remarks/>
    public uint CRLSerialNumber
    {
        get
        {
            return this.cRLSerialNumberField;
        }
        set
        {
            this.cRLSerialNumberField = value;
        }
    }

    /// <remarks/>
    public DateTime CRLThisUpdate
    {
        get
        {
            return this.cRLThisUpdateField;
        }
        set
        {
            this.cRLThisUpdateField = value;
        }
    }
}

【讨论】：

嗨。有用！非常感谢。一件事 - 它需要在 Deserializer 类中用 StreamReader 替换 StringReader。

【解决方案2】：

您需要各种元素的实例成员，而不仅仅是类型。例如：

[XmlRoot("VerificationResult")]
public class VerResult
{
    public Result Result { get; set; }
    public Description Description { get; set; }
    public string SignatureID { get; set; }
    public DateTime SigningTime { get; set; }
    public DateTime VerificationTime { get; set; }
    public SigningCertificate SigningCertificate { get; set; }
    public RevocationInfo RevocationInfo { get; set; }
}

（这里我已经将嵌套类型移出，以避免命名冲突）

完成后：数据可以很好地反序列化。

【讨论】：

不完全理解 - 有公共课程前。 Result , 带有私有 Result?
@xavrasx 您正在声明类型，但您需要具有这些类型的 members （理想情况下是属性）；您目前没有；此代码添加它们
感谢您的解释。现在明白了：）最好的问候