XmlAttributeOverrides クラス
アセンブリ: System.Xml (system.xml.dll 内)
構文
解説
XmlAttributeOverrides を使用すると、オブジェクトのセットをシリアル化する既定の方法を XmlSerializer でオーバーライドできるようになります。この方法でシリアル化をオーバーライドすることには 2 つの利点があります。第 1 に、DLL にアクセスしなくても、DLL 内のオブジェクトのシリアル化の制御および増大ができます。第 2 に、シリアル化できるクラスを 1 セット作成し、オブジェクトを複数の方法でシリアル化できます。たとえば、あるクラス インスタンスのメンバを XML 要素としてシリアル化する代わりに XML 属性としてシリアル化して、トランスポート効率の高いドキュメントにできます。
XmlAttributeOverrides オブジェクトを作成した後、このオブジェクトを引数として XmlSerializer コンストラクタに渡します。こうして得られた XmlSerializer は、XmlAttributeOverrides が保持しているデータを使用して、オブジェクトがどのようにシリアル化されるかを制御する属性をオーバーライドします。このようなオーバーライドを実現するために、XmlAttributeOverrides には、オーバーライド対象のオブジェクト型のコレクションの他、それらの各オブジェクト型に関連付けられている XmlAttributes オブジェクトが格納されます。XmlAttributes オブジェクトそのものに、フィールド、プロパティ、またはクラスをどのようにシリアル化するかを制御する、属性オブジェクトの適切なセットが含まれています。
XmlAttributeOverrides オブジェクトの作成および使用手順は次のとおりです。
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オーバーライドされているオブジェクトに対して適切な属性オブジェクトを作成します。たとえば、フィールドまたはプロパティをオーバーライドするには、新しい派生型を使用して XmlElementAttribute を作成します。オプションとして、新しい ElementName または Namespace を割り当て、基本クラスの属性名または名前空間をオーバーライドすることもできます。
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適切な XmlAttributes のプロパティまたはコレクションに属性オブジェクトを追加します。たとえば、オーバーライドされるメンバ名を指定して XmlAttributes オブジェクトの XmlElements コレクションに XmlElementAttribute を追加します。
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Add メソッドを使用して XmlAttributes オブジェクトを XmlAttributeOverrides オブジェクトに追加します。オーバーライドされる予定のオブジェクトが XmlRootAttribute または XmlTypeAttribute である場合は、オーバーライドされるオブジェクトの型を指定するだけで済みます。ただし、フィールドまたはプロパティをオーバーライドする場合は、オーバーライドされるメンバの名前も指定する必要があります。
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XmlSerializer を構築するときは、XmlAttributeOverrides を XmlSerializer コンストラクタに渡します。
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結果として得られた XmlSerializer を使用して、派生クラス オブジェクトのシリアル化または逆シリアル化を行います。
Orchestra という名前のクラスをシリアル化する例を次に示します。この例には、Instruments オブジェクトの配列を返す Instruments という名前の単一のフィールドが含まれています。Brass という名前の 2 番目のクラスが Instruments クラスから継承されます。この例では、XmlAttributeOverrides クラスのインスタンスを使用して Instruments フィールドをオーバーライドし、このフィールドが Brass オブジェクトを受け入れるようにします。
Option Explicit Option Strict Imports System Imports System.IO Imports System.Xml.Serialization Imports Microsoft.VisualBasic Public Class Orchestra Public Instruments() As Instrument End Class Public Class Instrument Public Name As String End Class Public Class Brass Inherits Instrument Public IsValved As Boolean End Class Public Class Run Public Shared Sub Main() Dim test As New Run() test.SerializeObject("Override.xml") test.DeserializeObject("Override.xml") End Sub Public Sub SerializeObject(ByVal filename As String) ' Each overridden field, property, or type requires ' an XmlAttributes object. Dim attrs As New XmlAttributes() ' Create an XmlElementAttribute to override the ' field that returns Instrument objects. The overridden field ' returns Brass objects instead. Dim attr As New XmlElementAttribute() attr.ElementName = "Brass" attr.Type = GetType(Brass) ' Add the element to the collection of elements. attrs.XmlElements.Add(attr) ' Create the XmlAttributeOverrides object. Dim attrOverrides As New XmlAttributeOverrides() ' Add the type of the class that contains the overridden ' member and the XmlAttributes to override it with to the ' XmlAttributeOverrides object. attrOverrides.Add(GetType(Orchestra), "Instruments", attrs) ' Create the XmlSerializer using the XmlAttributeOverrides. Dim s As New XmlSerializer(GetType(Orchestra), attrOverrides) ' Writing the file requires a TextWriter. Dim writer As New StreamWriter(filename) ' Create the object that will be serialized. Dim band As New Orchestra() ' Create an object of the derived type. Dim i As New Brass() i.Name = "Trumpet" i.IsValved = True Dim myInstruments() As Instrument = {i} band.Instruments = myInstruments ' Serialize the object. s.Serialize(writer, band) writer.Close() End Sub Public Sub DeserializeObject(filename As String) Dim attrOverrides As New XmlAttributeOverrides() Dim attrs As New XmlAttributes() ' Create an XmlElementAttribute to override the Instrument. Dim attr As New XmlElementAttribute() attr.ElementName = "Brass" attr.Type = GetType(Brass) ' Add the XmlElementAttribute to the collection of objects. attrs.XmlElements.Add(attr) attrOverrides.Add(GetType(Orchestra), "Instruments", attrs) ' Create the XmlSerializer using the XmlAttributeOverrides. Dim s As New XmlSerializer(GetType(Orchestra), attrOverrides) Dim fs As New FileStream(filename, FileMode.Open) Dim band As Orchestra = CType(s.Deserialize(fs), Orchestra) Console.WriteLine("Brass:") ' The difference between deserializing the overridden ' XML document and serializing it is this: To read the derived ' object values, you must declare an object of the derived type ' (Brass), and cast the Instrument instance to it. Dim b As Brass Dim i As Instrument For Each i In band.Instruments b = CType(i, Brass) Console.WriteLine(b.Name & ControlChars.Cr & b.IsValved) Next i End Sub End Class
using System; using System.IO; using System.Xml.Serialization; public class Orchestra { public Instrument[] Instruments; } public class Instrument { public string Name; } public class Brass:Instrument { public bool IsValved; } public class Run { public static void Main() { Run test = new Run(); test.SerializeObject("Override.xml"); test.DeserializeObject("Override.xml"); } public void SerializeObject(string filename) { /* Each overridden field, property, or type requires an XmlAttributes object. */ XmlAttributes attrs = new XmlAttributes(); /* Create an XmlElementAttribute to override the field that returns Instrument objects. The overridden field returns Brass objects instead. */ XmlElementAttribute attr = new XmlElementAttribute(); attr.ElementName = "Brass"; attr.Type = typeof(Brass); // Add the element to the collection of elements. attrs.XmlElements.Add(attr); // Create the XmlAttributeOverrides object. XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides(); /* Add the type of the class that contains the overridden member and the XmlAttributes to override it with to the XmlAttributeOverrides object. */ attrOverrides.Add(typeof(Orchestra), "Instruments", attrs); // Create the XmlSerializer using the XmlAttributeOverrides. XmlSerializer s = new XmlSerializer(typeof(Orchestra), attrOverrides); // Writing the file requires a TextWriter. TextWriter writer = new StreamWriter(filename); // Create the object that will be serialized. Orchestra band = new Orchestra(); // Create an object of the derived type. Brass i = new Brass(); i.Name = "Trumpet"; i.IsValved = true; Instrument[] myInstruments = {i}; band.Instruments = myInstruments; // Serialize the object. s.Serialize(writer,band); writer.Close(); } public void DeserializeObject(string filename) { XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides(); XmlAttributes attrs = new XmlAttributes(); // Create an XmlElementAttribute to override the Instrument. XmlElementAttribute attr = new XmlElementAttribute(); attr.ElementName = "Brass"; attr.Type = typeof(Brass); // Add the XmlElementAttribute to the collection of objects. attrs.XmlElements.Add(attr); attrOverrides.Add(typeof(Orchestra), "Instruments", attrs); // Create the XmlSerializer using the XmlAttributeOverrides. XmlSerializer s = new XmlSerializer(typeof(Orchestra), attrOverrides); FileStream fs = new FileStream(filename, FileMode.Open); Orchestra band = (Orchestra) s.Deserialize(fs); Console.WriteLine("Brass:"); /* The difference between deserializing the overridden XML document and serializing it is this: To read the derived object values, you must declare an object of the derived type (Brass), and cast the Instrument instance to it. */ Brass b; foreach(Instrument i in band.Instruments) { b = (Brass)i; Console.WriteLine( b.Name + "\n" + b.IsValved); } } }
#using <System.Xml.dll> #using <System.dll> using namespace System; using namespace System::IO; using namespace System::Xml::Serialization; public ref class Instrument { public: String^ Name; }; public ref class Brass: public Instrument { public: bool IsValved; }; public ref class Orchestra { public: array<Instrument^>^Instruments; }; void SerializeObject( String^ filename ) { /* Each overridden field, property, or type requires an XmlAttributes object. */ XmlAttributes^ attrs = gcnew XmlAttributes; /* Create an XmlElementAttribute to override the field that returns Instrument objects. The overridden field returns Brass objects instead. */ XmlElementAttribute^ attr = gcnew XmlElementAttribute; attr->ElementName = "Brass"; attr->Type = Brass::typeid; // Add the element to the collection of elements. attrs->XmlElements->Add( attr ); // Create the XmlAttributeOverrides object. XmlAttributeOverrides^ attrOverrides = gcnew XmlAttributeOverrides; /* Add the type of the class that contains the overridden member and the XmlAttributes to override it with to the XmlAttributeOverrides object. */ attrOverrides->Add( Orchestra::typeid, "Instruments", attrs ); // Create the XmlSerializer using the XmlAttributeOverrides. XmlSerializer^ s = gcnew XmlSerializer( Orchestra::typeid,attrOverrides ); // Writing the file requires a TextWriter. TextWriter^ writer = gcnew StreamWriter( filename ); // Create the object that will be serialized. Orchestra^ band = gcnew Orchestra; // Create an object of the derived type. Brass^ i = gcnew Brass; i->Name = "Trumpet"; i->IsValved = true; array<Instrument^>^myInstruments = {i}; band->Instruments = myInstruments; // Serialize the object. s->Serialize( writer, band ); writer->Close(); } void DeserializeObject( String^ filename ) { XmlAttributeOverrides^ attrOverrides = gcnew XmlAttributeOverrides; XmlAttributes^ attrs = gcnew XmlAttributes; // Create an XmlElementAttribute to override the Instrument. XmlElementAttribute^ attr = gcnew XmlElementAttribute; attr->ElementName = "Brass"; attr->Type = Brass::typeid; // Add the XmlElementAttribute to the collection of objects. attrs->XmlElements->Add( attr ); attrOverrides->Add( Orchestra::typeid, "Instruments", attrs ); // Create the XmlSerializer using the XmlAttributeOverrides. XmlSerializer^ s = gcnew XmlSerializer( Orchestra::typeid,attrOverrides ); FileStream^ fs = gcnew FileStream( filename,FileMode::Open ); Orchestra^ band = dynamic_cast<Orchestra^>(s->Deserialize( fs )); Console::WriteLine( "Brass:" ); /* The difference between deserializing the overridden XML document and serializing it is this: To read the derived object values, you must declare an object of the derived type (Brass), and cast the Instrument instance to it. */ Brass^ b; System::Collections::IEnumerator^ myEnum = band->Instruments->GetEnumerator(); while ( myEnum->MoveNext() ) { Instrument^ i = safe_cast<Instrument^>(myEnum->Current); b = dynamic_cast<Brass^>(i); Console::WriteLine( "{0}\n{1}", b->Name, b->IsValved ); } } int main() { SerializeObject( "Override.xml" ); DeserializeObject( "Override.xml" ); }
import System.*; import System.IO.*; import System.Xml.Serialization.*; public class Orchestra { public Instrument instruments[]; } //Orchestra public class Instrument { public String name; } //Instrument public class Brass extends Instrument { public boolean isValved; } //Brass public class Run { public static void main(String[] args) { Run test = new Run(); test.SerializeObject("Override.xml"); test.DeserializeObject("Override.xml"); } //main public void SerializeObject(String fileName) { /* Each overridden field, property, or type requires an XmlAttributes object. */ XmlAttributes attrs = new XmlAttributes(); /* Create an XmlElementAttribute to override the field that returns Instrument objects. The overridden field returns Brass objects instead. */ XmlElementAttribute attr = new XmlElementAttribute(); attr.set_ElementName("Brass"); attr.set_Type(Brass.class.ToType()); // Add the element to the collection of elements. attrs.get_XmlElements().Add(attr); // Create the XmlAttributeOverrides object. XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides(); /* Add the type of the class that contains the overridden member and the XmlAttributes to override it with to the XmlAttributeOverrides object. */ attrOverrides.Add(Orchestra.class.ToType(), "instruments", attrs); // Create the XmlSerializer using the XmlAttributeOverrides. XmlSerializer s = new XmlSerializer(Orchestra.class.ToType(), attrOverrides); // Writing the file requires a TextWriter. TextWriter writer = new StreamWriter(fileName); // Create the object that will be serialized. Orchestra band = new Orchestra(); // Create an object of the derived type. Brass i = new Brass(); i.name = "Trumpet"; i.isValved = true; Instrument myInstruments[] ={ i }; band.instruments = myInstruments; // Serialize the object. s.Serialize(writer, band); writer.Close(); } //SerializeObject public void DeserializeObject(String fileName) { XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides(); XmlAttributes attrs = new XmlAttributes(); // Create an XmlElementAttribute to override the Instrument. XmlElementAttribute attr = new XmlElementAttribute(); attr.set_ElementName("Brass"); attr.set_Type(Brass.class.ToType()); // Add the XmlElementAttribute to the collection of objects. attrs.get_XmlElements().Add(attr); attrOverrides.Add(Orchestra.class.ToType(), "instruments", attrs); // Create the XmlSerializer using the XmlAttributeOverrides. XmlSerializer s = new XmlSerializer(Orchestra.class.ToType(), attrOverrides); FileStream fs = new FileStream(fileName, FileMode.Open); Orchestra band = (Orchestra)s.Deserialize(fs); Console.WriteLine("Brass:"); /* The difference between deserializing the overridden XML document and serializing it is this: To read the derived object values, you must declare an object of the derived type (Brass), and cast the Instrument instance to it. */ Brass b; for (int iCtr = 0; iCtr < band.instruments.length; iCtr++) { Instrument i = (Instrument)band.instruments.get_Item(iCtr); b = (Brass)i; Console.WriteLine(b.name + "\n" + System.Convert.ToString(b.isValved)); } } //DeserializeObject } //Run
System.Xml.Serialization.XmlAttributeOverrides
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参照
- XmlAttributeOverrides クラスのページへのリンク