SerializationInfo.GetValue(String, Type) Metodo

Definizione

Recupera un valore dall'archivio SerializationInfo.Retrieves a value from the SerializationInfo store.

public:
 System::Object ^ GetValue(System::String ^ name, Type ^ type);
public object GetValue (string name, Type type);
member this.GetValue : string * Type -> obj

Parametri

name
String

Nome associato al valore da recuperare.The name associated with the value to retrieve.

type
Type

Tipo Type del valore da recuperare.The Type of the value to retrieve. Se il valore memorizzato non può essere convertito in questo tipo, verrà generata un'eccezione InvalidCastException.If the stored value cannot be converted to this type, the system will throw a InvalidCastException.

Restituisce

Oggetto del tipo Type specificato associato a name.The object of the specified Type associated with name.

Eccezioni

name o type è null.name or type is null.

Il valore associato a name non può essere convertito in type.The value associated with name cannot be converted to type.

Non è possibile trovare un elemento con il nome specificato nell'istanza corrente.An element with the specified name is not found in the current instance.

Esempi

Nell'esempio di codice riportato di seguito viene illustrato GetValue l'utilizzo del metodo:The following code example demonstrates the use of the GetValue method:

// A serializable LinkedList example.  For the full LinkedList implementation
// see the Serialization sample.
[Serializable]
ref class LinkedList: public ISerializable
{
private:
   Node^ m_head;
   Node^ m_tail;

   // Serializes the object.
public:
   virtual void GetObjectData( SerializationInfo^ info, StreamingContext /*context*/ )
   {
      // Stores the m_head and m_tail references in the SerializationInfo info.
      info->AddValue( "head", m_head, m_head->GetType() );
      info->AddValue( "tail", m_tail, m_tail->GetType() );
   }

   // Constructor that is called automatically during deserialization.
private:
   // Reconstructs the object from the information in SerializationInfo info
   LinkedList( SerializationInfo^ info, StreamingContext /*context*/ )
   {
      Node^ temp = gcnew Node( 0 );
      // Retrieves the values of Type temp.GetType() from SerializationInfo info
      m_head = dynamic_cast<Node^>(info->GetValue( "head", temp->GetType() ));
      m_tail = dynamic_cast<Node^>(info->GetValue( "tail", temp->GetType() ));
   }
};
// A serializable LinkedList example.  For the full LinkedList implementation
// see the Serialization sample.
[Serializable()]
class LinkedList: ISerializable {

   public static void Main() {}

   Node m_head = null;
   Node m_tail = null;
   
   // Serializes the object.
   [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter=true)]
   public void GetObjectData(SerializationInfo info, StreamingContext context){
      // Stores the m_head and m_tail references in the SerializationInfo info.
      info.AddValue("head", m_head, m_head.GetType());
      info.AddValue("tail", m_tail, m_tail.GetType());
   }
   
   // Constructor that is called automatically during deserialization.
   // Reconstructs the object from the information in SerializationInfo info
   [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter=true)]
   private LinkedList(SerializationInfo info, StreamingContext context)
   {      
      Node temp = new Node(0);
      // Retrieves the values of Type temp.GetType() from SerializationInfo info
      m_head = (Node)info.GetValue("head", temp.GetType());
      m_tail = (Node)info.GetValue("tail", temp.GetType());
   }
}
' A serializable LinkedList example.  For the full LinkedList implementation
' see the Serialization sample.
<Serializable()> Class LinkedList
    Implements ISerializable

    Public Shared Sub Main()
    End Sub

    Private m_head As Node = Nothing
    Private m_tail As Node = Nothing    
    
    ' Serializes the object.
    Public Sub GetObjectData(info As SerializationInfo, _
    context As StreamingContext) Implements ISerializable.GetObjectData
    
        ' Stores the m_head and m_tail references in the SerializationInfo info.
        info.AddValue("head", m_head, m_head.GetType())
        info.AddValue("tail", m_tail, m_tail.GetType())
    End Sub
    
    
    ' Constructor that is called automatically during deserialization.
    ' Reconstructs the object from the information in SerializationInfo info.
    Private Sub New(info As SerializationInfo, context As StreamingContext)
        Dim temp As New Node(0)
        ' Retrieves the values of Type temp.GetType() from SerializationInfo info.
        m_head = CType(info.GetValue("head", temp.GetType()), Node)
        m_tail = CType(info.GetValue("tail", temp.GetType()), Node)
    End Sub
End Class

Commenti

Se i dati archiviati in SerializationInfo sono del tipo richiesto (o una delle relative classi derivate), tale valore viene restituito direttamente.If the data stored in the SerializationInfo is of the type requested (or one of its derived classes), that value is returned directly. In caso IFormatterConverter.Convert contrario, viene chiamato per convertirlo nel tipo appropriato.Otherwise, IFormatterConverter.Convert is called to convert it to the appropriate type.

Il cast del valore restituito GetValue dal metodo può sempre essere eseguito in modo sicuro nel tipo specificato type nel parametro.The value returned by the GetValue method can always be safely cast to the type specified in the type parameter.

Si applica a