抑制xsi：nil，但仍然显示在.NET中序列化时显示空元素

Question

我有一个C＃类，具有20 +字符串属性。我将其中的四分之一设置为实际值。我想序列化类，并得到

<EmptyAttribute></EmptyAttribute> 

的输出属性

public string EmptyAttribute {get;set;} 

我不希望输出为

<EmptyAttribute xsi:nil="true"></EmptyAttribute> 

我使用下面的类

public class XmlTextWriterFull : XmlTextWriter 
{ 
    public XmlTextWriterFull(string filename) : base(filename,Encoding.UTF8) { } 

    public override void WriteEndElement() 
    { 
     base.WriteFullEndElement(); 
     base.WriteRaw(Environment.NewLine); 
    } 
} 

这样我可以得到完整的标签。我只是不知道如何摆脱xsi：nil。

Answer 1

我实际上能够弄清楚这一点。我知道它有点在某些方面是黑客攻击的，但是这是我得到它的工作

System.Xml.Serialization.XmlSerializer x = new System.Xml.Serialization.XmlSerializer(header.GetType()); 
     XmlTextWriterFull writer = new XmlTextWriterFull(FilePath); 
     x.Serialize(writer, header); 
     writer.Flush(); 
     writer.BaseStream.Dispose(); 
     string xml = File.ReadAllText(FilePath); 
     xml = xml.Replace(" xsi:nil=\"true\"", ""); 
     File.WriteAllText(FilePath, xml); 

希望这可以帮助其他人了

Answer 2

的方式有XmlSerializer连载的属性不添加xsi:nil="true"属性如下所示：

[XmlRoot("MyClassWithNullableProp", Namespace="urn:myNamespace", IsNullable = false)] 
public class MyClassWithNullableProp 
{ 
    public MyClassWithNullableProp() 
    { 
     this._namespaces = new XmlSerializerNamespaces(new XmlQualifiedName[] { 
      new XmlQualifiedName(string.Empty, "urn:myNamespace") // Default Namespace 
     }); 
    } 

    [XmlElement("Property1", Namespace="urn:myNamespace", IsNullable = false)] 
    public string Property1 
    { 
     get 
     { 
      // To make sure that no element is generated, even when the value of the 
      // property is an empty string, return null. 
      return string.IsNullOrEmpty(this._property1) ? null : this._property1; 
     } 
     set { this._property1 = value; } 
    } 
    private string _property1; 

    // To do the same for value types, you need a "helper property, as demonstrated below. 
    // First, the regular property. 
    [XmlIgnore] // The serializer won't serialize this property properly. 
    public int? MyNullableInt 
    { 
     get { return this._myNullableInt; } 
     set { this._myNullableInt = value; } 
    } 
    private int? _myNullableInt; 

    // And now the helper property that the serializer will use to serialize it. 
    [XmlElement("MyNullableInt", Namespace="urn:myNamespace", IsNullable = false)] 
    public string XmlMyNullableInt 
    { 
     get 
     { 
      return this._myNullableInt.HasValue? 
       this._myNullableInt.Value.ToString() : null; 
     } 
     set { this._myNullableInt = int.Parse(value); } // You should do more error checking... 
    } 

    // Now, a string property where you want an empty element to be displayed, but no 
    // xsi:nil. 
    [XmlElement("MyEmptyString", Namespace="urn:myNamespace", IsNullable = false)] 
    public string MyEmptyString 
    { 
     get 
     { 
      return string.IsNullOrEmpty(this._myEmptyString)? 
       string.Empty : this._myEmptyString; 
     } 
     set { this._myEmptyString = value; } 
    } 
    private string _myEmptyString; 

    // Now, a value type property for which you want an empty tag, and not, say, 0, or 
    // whatever default value the framework gives the type. 
    [XmlIgnore] 
    public float? MyEmptyNullableFloat 
    { 
     get { return this._myEmptyNullableFloat; } 
     set { this._myEmptyNullableFloat = value; } 
    } 
    private float? _myEmptyNullableFloat; 

    // The helper property for serialization. 
    public string XmlMyEmptyNullableFloat 
    { 
     get 
     { 
      return this._myEmptyNullableFloat.HasValue ? 
       this._myEmptyNullableFloat.Value.ToString() : string.Empty; 
     } 
     set 
     { 
      if (!string.IsNullOrEmpty(value)) 
       this._myEmptyNullableFloat = float.Parse(value); 
     } 
    } 

    [XmlNamespaceDeclarations] 
    public XmlSerializerNamespaces Namespaces 
    { 
     get { return this._namespaces; } 
    } 
    private XmlSerializerNamespaces _namespaces; 
} 

现在，实例化这个类并对其进行序列化。

// I just wanted to show explicitly setting all the properties to null... 
MyClassWithNullableProp myClass = new MyClassWithNullableProp() { 
    Property1 = null, 
    MyNullableInt = null, 
    MyEmptyString = null, 
    MyEmptyNullableFloat = null 
}; 

// Serialize it. 
// You'll need to setup some backing store for the text writer below... 
// a file, memory stream, something... 
XmlTextWriter writer = XmlTextWriter(...) // Instantiate a text writer. 

XmlSerializer xs = new XmlSerializer(typeof(MyClassWithNullableProp), 
    new XmlRootAttribute("MyClassWithNullableProp") { 
     Namespace="urn:myNamespace", 
     IsNullable = false 
    } 
); 

xs.Serialize(writer, myClass, myClass.Namespaces); 

检索XmlTextWriter的内容后，你应该有以下的输出：

<MyClassWithNullableProp> 
    <MyEmptyString /> 
    <MyEmptyNullableFloat /> 
</MyClassWithNullableProp> 

我希望这清楚地说明内置.NET框架XmlSerializer可用于性能序列化一个空元素，即使属性值为空（或者其他值不想序列化）。另外，我已经展示了如何确保null属性完全没有序列化。有一点需要注意，如果您应用XmlElementAttribute并将该属性的IsNullable属性设置为true，那么当属性为null（除非在其他位置重写）时，该属性将与xsi:nil属性串行化。