DnsPermission.FromXml(SecurityElement) Method

Definition

Namespace:

System.Net

Assembly:

System.Security.Permissions.dll

Reconstructs a DnsPermission instance from an XML encoding.

public:
 override void FromXml(System::Security::SecurityElement ^ securityElement);

public override void FromXml (System.Security.SecurityElement securityElement);

override this.FromXml : System.Security.SecurityElement -> unit

Public Overrides Sub FromXml (securityElement As SecurityElement)

Parameters

securityElement

SecurityElement

The XML encoding to use to reconstruct the DnsPermission instance.

Exceptions

ArgumentNullException

securityElement is null.

ArgumentException

securityElement is not a DnsPermission element.

Examples

The following example reconstructs a DnsPermission instance from an XML encoding.

public:
   void ConstructDnsPermission()
   {
      try
      {
         // Create a DnsPermission instance.
         DnsPermission^ permission = gcnew DnsPermission( PermissionState::None );
         // Create a SecurityElement instance by calling the ToXml method on the
         // DnsPermission instance.
         // Print its attributes, which hold the  XML encoding of the DnsPermission
         // instance.
         Console::WriteLine( "Attributes and Values of 'DnsPermission' instance :" );
         PrintKeysAndValues( permission->ToXml()->Attributes );
         
         // Create a SecurityElement instance.
         SecurityElement^ securityElementObj = gcnew SecurityElement( "IPermission" );
         // Add attributes and values of the SecurityElement instance corresponding to
         // the permission instance.
         securityElementObj->AddAttribute( "version", "1" );
         securityElementObj->AddAttribute( "Unrestricted", "true" );
         securityElementObj->AddAttribute( "class", "System.Net.DnsPermission" );
         
         // Reconstruct a DnsPermission instance from an XML encoding.
         DnsPermission^ permission1 = gcnew DnsPermission( PermissionState::None );
         permission1->FromXml( securityElementObj );
         
         // Print the attributes and values of the constructed DnsPermission Object*.
         Console::WriteLine( "After reconstruction Attributes and Values of new DnsPermission instance :" );
         PrintKeysAndValues( permission1->ToXml()->Attributes );
      }
      catch ( NullReferenceException^ e ) 
      {
         Console::WriteLine( "NullReferenceException caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
      catch ( SecurityException^ e ) 
      {
         Console::WriteLine( "SecurityException caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
      catch ( ArgumentNullException^ e ) 
      {
         Console::WriteLine( "ArgumentNullException caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
      catch ( Exception^ e ) 
      {
         Console::WriteLine( "Exception caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
   }

private:
   void PrintKeysAndValues( Hashtable^ myList )
   {
      // Get the enumerator that can iterate through the hash table.
      IDictionaryEnumerator^ myEnumerator = myList->GetEnumerator();
      Console::WriteLine( "\t-KEY-\t-VALUE-" );
      while ( myEnumerator->MoveNext() )
      {
         Console::WriteLine( "\t {0}:\t {1}", myEnumerator->Key, myEnumerator->Value );
      }
      Console::WriteLine();
   }

public void ConstructDnsPermission() {
  try
  {
    // Create a DnsPermission instance.
    DnsPermission permission = new DnsPermission(PermissionState.None);
    // Create a SecurityElement instance by calling the ToXml method on the
    // DnsPermission instance.
    // Print its attributes, which hold the  XML encoding of the DnsPermission
    // instance.
    Console.WriteLine("Attributes and Values of 'DnsPermission' instance :");
    PrintKeysAndValues(permission.ToXml().Attributes);

    // Create a SecurityElement instance.
    SecurityElement securityElementObj = new SecurityElement("IPermission");
    // Add attributes and values of the SecurityElement instance corresponding to
    // the permission instance.
    securityElementObj.AddAttribute("version", "1");
    securityElementObj.AddAttribute("Unrestricted", "true");
    securityElementObj.AddAttribute("class","System.Net.DnsPermission");

    // Reconstruct a DnsPermission instance from an XML encoding.
      DnsPermission permission1 = new DnsPermission(PermissionState.None);
    permission1.FromXml(securityElementObj);

    // Print the attributes and values of the constructed DnsPermission object.
    Console.WriteLine("After reconstruction Attributes and Values of new DnsPermission instance :");
    PrintKeysAndValues(permission1.ToXml().Attributes);
  }
  catch(NullReferenceException e)
  {
    Console.WriteLine("NullReferenceException caught!!!");
    Console.WriteLine("Source : " + e.Source);
    Console.WriteLine("Message : " + e.Message);
  }
  catch(SecurityException e)
  {
    Console.WriteLine("SecurityException caught!!!");
    Console.WriteLine("Source : " + e.Source);
    Console.WriteLine("Message : " + e.Message);
  }
  catch(ArgumentNullException e)
  {
    Console.WriteLine("ArgumentNullException caught!!!");
    Console.WriteLine("Source : " + e.Source);
    Console.WriteLine("Message : " + e.Message);
  }
  catch(Exception e)
  {
    Console.WriteLine("Exception caught!!!");
    Console.WriteLine("Source : " + e.Source);
    Console.WriteLine("Message : " + e.Message);
  }
}

private void PrintKeysAndValues(Hashtable myList) {
   // Get the enumerator that can iterate through the hash table.
   IDictionaryEnumerator myEnumerator = myList.GetEnumerator();
   Console.WriteLine("\t-KEY-\t-VALUE-");
   while (myEnumerator.MoveNext())
      Console.WriteLine("\t{0}:\t{1}", myEnumerator.Key, myEnumerator.Value);
      Console.WriteLine();
}

Public Sub ConstructDnsPermission()
    Try
        ' Create a DnsPermission instance.
        Dim permission As New DnsPermission(PermissionState.None)
        ' Create a SecurityElement instance by calling the ToXml method on the
        ' DnsPermission instance and print its attributes, 
        ' which hold the  XML encoding of the DnsPermission instance.
        Console.WriteLine("Attributes and Values of 'DnsPermission' instance :")
        PrintKeysAndValues(permission.ToXml().Attributes)
        
        ' Create a SecurityElement instacnce .
        Dim securityElementObj As New SecurityElement("IPermission")
        ' Add attributes and values of the SecurityElement instance corresponding to
        ' the permission instance.
        securityElementObj.AddAttribute("version", "1")
        securityElementObj.AddAttribute("Unrestricted", "true")
        securityElementObj.AddAttribute("class", "System.Net.DnsPermission")
        
        ' Reconstruct a DnsPermission instance from an XML encoding.
        Dim permission1 As New DnsPermission(PermissionState.None)
        permission1.FromXml(securityElementObj)
        
        ' Print the attributes and values of the constructed DnsPermission object.
        Console.WriteLine("After reconstruction Attributes and Values of new DnsPermission instance :")
        PrintKeysAndValues(permission1.ToXml().Attributes)
    Catch e As NullReferenceException
        Console.WriteLine("NullReferenceException caught!!!")
        Console.WriteLine(("Source : " + e.Source))
        Console.WriteLine(("Message : " + e.Message))
    Catch e As SecurityException
        Console.WriteLine("SecurityException caught!!!")
        Console.WriteLine(("Source : " + e.Source))
        Console.WriteLine(("Message : " + e.Message))
    Catch e As ArgumentNullException
        Console.WriteLine("ArgumentNullException caught!!!")
        Console.WriteLine(("Source : " + e.Source))
        Console.WriteLine(("Message : " + e.Message))
    Catch e As Exception
        Console.WriteLine("Exception caught!!!")
        Console.WriteLine(("Source : " + e.Source))
        Console.WriteLine(("Message : " + e.Message))
    End Try
End Sub


Private Sub PrintKeysAndValues(myList As Hashtable)
    ' Get the enumerator that can iterate through the hash table.
    Dim myEnumerator As IDictionaryEnumerator = myList.GetEnumerator()
    Console.WriteLine(ControlChars.Tab + "-KEY-" + ControlChars.Tab + "-VALUE-")
    While myEnumerator.MoveNext()
        Console.WriteLine(ControlChars.Tab + "{0}:" + ControlChars.Tab + "{1}", myEnumerator.Key, myEnumerator.Value)
    End While
    Console.WriteLine()
End Sub

Remarks

The FromXml method reconstructs a DnsPermission instance from an XML encoding defined by the SecurityElement class.

Use the ToXml method to XML-encode the DnsPermission instance, including state information.

See also

• SecurityElement