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DnsPermission.FromXml Method

Reconstructs a DnsPermission instance from an XML encoding.

Namespace:  System.Net
Assembly:  System (in System.dll)

'Declaration
Public Overrides Sub FromXml ( _
	securityElement As SecurityElement _
)
'Usage
Dim instance As DnsPermission 
Dim securityElement As SecurityElement

instance.FromXml(securityElement)

Parameters

securityElement
Type: System.Security.SecurityElement

The XML encoding to use to reconstruct the DnsPermission instance.

Implements

ISecurityEncodable.FromXml(SecurityElement)

ExceptionCondition
ArgumentNullException

securityElement is Nothing.

ArgumentException

securityElement is not a DnsPermission element.

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.

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

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 
        ' teh 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 'ConstructDnsPermission


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 'PrintKeysAndValues
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(S"Attributes and Values of 'DnsPermission' instance :");
         PrintKeysAndValues(permission->ToXml()->Attributes);

         // Create a SecurityElement instance.
         SecurityElement* securityElementObj = new SecurityElement(S"IPermission");
         // Add attributes and values of the SecurityElement instance corresponding to
         // the permission instance.
         securityElementObj->AddAttribute(S"version", S"1");
         securityElementObj->AddAttribute(S"Unrestricted", S"true");
         securityElementObj->AddAttribute(S"class", S"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(S"After reconstruction Attributes and Values of new DnsPermission instance :");
         PrintKeysAndValues(permission1->ToXml()->Attributes);
      }
      catch (NullReferenceException* e)
      {
         Console::WriteLine(S"NullReferenceException caught!!!");
         Console::WriteLine(S"Source : {0}", e->Source);
         Console::WriteLine(S"Message : {0}", e->Message);
      }
      catch (SecurityException* e)
      {
         Console::WriteLine(S"SecurityException caught!!!");
         Console::WriteLine(S"Source : {0}", e->Source);
         Console::WriteLine(S"Message : {0}", e->Message);
      }
      catch (ArgumentNullException* e)
      {
         Console::WriteLine(S"ArgumentNullException caught!!!");
         Console::WriteLine(S"Source : {0}", e->Source);
         Console::WriteLine(S"Message : {0}", e->Message);
      }
      catch (Exception* e)
      {
         Console::WriteLine(S"Exception caught!!!");
         Console::WriteLine(S"Source : {0}", e->Source);
         Console::WriteLine(S"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(S"\t-KEY-\t-VALUE-");
      while (myEnumerator->MoveNext())
         Console::WriteLine(S"\t {0}:\t {1}", 
         myEnumerator->Key, myEnumerator->Value);
      Console::WriteLine();
   }

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

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