XmlChoiceIdentifierAttribute Constructor ()

 

Initializes a new instance of the XmlChoiceIdentifierAttribute class.

Namespace:   System.Xml.Serialization
Assembly:  System.Xml (in System.Xml.dll)

public:
XmlChoiceIdentifierAttribute()

The following example serializes a class named Choices that includes two fields, MyChoice and ManyChoices. The XmlChoiceIdentifierAttribute is applied to each field that specifies (through the MemberName property) another class member that gets or sets an enumeration that detects the member value. The MyChoice field can be set to a single value, with a corresponding enumeration member found in the EnumType field. The ManyChoices field returns an array of objects. The ChoiceArray field returns an array of enumeration values. For each array member in the ManyChoices field, a corresponding member is found in the array returned by the ChoiceArray field.

#using <System.dll>
#using <System.xml.dll>

using namespace System;
using namespace System::Xml;
using namespace System::Xml::Serialization;
using namespace System::IO;

[XmlType(IncludeInSchema=false)]

public enum class ItemChoiceType
{
   None, Word, Number, DecimalNumber
};

public enum class MoreChoices
{
   None, Item, Amount, Temp
};

public ref class Choices
{
public:

   // The MyChoice field can be set to any one of 
   // the types below. 

   [XmlChoiceIdentifier("EnumType")]
   [XmlElement("Word",String::typeid)]
   [XmlElement("Number",Int32::typeid)]
   [XmlElement("DecimalNumber",Double::typeid)]
   Object^ MyChoice;

   // Don't serialize this field. The EnumType field
   // contains the enumeration value that corresponds
   // to the MyChoice field value.

   [XmlIgnore]
   ItemChoiceType EnumType;

   // The ManyChoices field can contain an array
   // of choices. Each choice must be matched to
   // an array item in the ChoiceArray field.

   [XmlChoiceIdentifier("ChoiceArray")]
   [XmlElement("Item",String::typeid)]
   [XmlElement("Amount",Int32::typeid)]
   [XmlElement("Temp",Double::typeid)]
   array<Object^>^ManyChoices;

   // TheChoiceArray field contains the enumeration
   // values, one for each item in the ManyChoices array.

   [XmlIgnore]
   array<MoreChoices>^ChoiceArray;
};

void SerializeObject( String^ filename );
void DeserializeObject( String^ filename );
int main()
{
   SerializeObject( "Choices.xml" );
   DeserializeObject( "Choices.xml" );
}

void SerializeObject( String^ filename )
{
   XmlSerializer^ mySerializer = gcnew XmlSerializer( Choices::typeid );
   TextWriter^ writer = gcnew StreamWriter( filename );
   Choices^ myChoices = gcnew Choices;

   // Set the MyChoice field to a string. Set the
   // EnumType to Word.
   myChoices->MyChoice = "Book";
   myChoices->EnumType = ItemChoiceType::Word;

   // Populate an object array with three items, one
   // of each enumeration type. Set the array to the 
   // ManyChoices field.
   array<Object^>^strChoices = {"Food",5,98.6};
   myChoices->ManyChoices = strChoices;

   // For each item in the ManyChoices array, add an
   // enumeration value.
   array<MoreChoices>^ itmChoices = {MoreChoices::Item,MoreChoices::Amount,MoreChoices::Temp};
   myChoices->ChoiceArray = itmChoices;
   mySerializer->Serialize( writer, myChoices );
   writer->Close();
}

void DeserializeObject( String^ filename )
{
   XmlSerializer^ ser = gcnew XmlSerializer( Choices::typeid );

   // A FileStream is needed to read the XML document.
   FileStream^ fs = gcnew FileStream( filename,FileMode::Open );
   Choices^ myChoices = safe_cast<Choices^>(ser->Deserialize( fs ));
   fs->Close();

   // Disambiguate the MyChoice value using the enumeration.
   if ( myChoices->EnumType == ItemChoiceType::Word )
   {
      Console::WriteLine( "Word: {0}", myChoices->MyChoice->ToString() );
   }
   else
   if ( myChoices->EnumType == ItemChoiceType::Number )
   {
      Console::WriteLine( "Number: {0}", myChoices->MyChoice->ToString() );
   }
   else
   if ( myChoices->EnumType == ItemChoiceType::DecimalNumber )
   {
      Console::WriteLine( "DecimalNumber: {0}", myChoices->MyChoice->ToString() );
   }

   // Disambiguate the ManyChoices values using the enumerations.
   for ( int i = 0; i < myChoices->ManyChoices->Length; i++ )
   {
      if ( myChoices->ChoiceArray[ i ] == MoreChoices::Item )
            Console::WriteLine( "Item: {0}", myChoices->ManyChoices[ i ] );
      else
      if ( myChoices->ChoiceArray[ i ] == MoreChoices::Amount )
            Console::WriteLine( "Amount: ", myChoices->ManyChoices[ i ]->ToString() );
      if ( myChoices->ChoiceArray[ i ] == MoreChoices::Temp )
            Console::WriteLine( "Temp: {0}", myChoices->ManyChoices[ i ]->ToString() );
   }
}

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Return to top
Show: