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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)
public void FromXml (
	SecurityElement securityElement
)
public override function FromXml (
	securityElement : SecurityElement
)

Parameters

securityElement

The XML encoding to use to reconstruct the DnsPermission instance.

Exception typeCondition

ArgumentNullException

securityElement is a null reference (Nothing in Visual Basic).

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("Attributes and Values of 'DnsPermission' "
            + "instance :");
        PrintKeysAndValues(permission.ToXml().get_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().get_Attributes());
    }
    catch (NullReferenceException e) {
        Console.WriteLine("NullReferenceException caught!!!");
        Console.WriteLine("Source : " + e.get_Source());
        Console.WriteLine("Message : " + e.get_Message());
    }
    catch (SecurityException e) {
        Console.WriteLine("SecurityException caught!!!");
        Console.WriteLine("Source : " + e.get_Source());
        Console.WriteLine("Message : " + e.get_Message());
    }
    catch (ArgumentNullException e) {
        Console.WriteLine("ArgumentNullException caught!!!");
        Console.WriteLine("Source : " + e.get_Source());
        Console.WriteLine("Message : " + e.get_Message());
    }
    catch (System.Exception e) {
        Console.WriteLine("Exception caught!!!");
        Console.WriteLine("Source : " + e.get_Source());
        Console.WriteLine("Message : " + e.get_Message());
    }
} //ConstructDnsPermission

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.get_Key(),
            myEnumerator.get_Value());
    }
    Console.WriteLine();
} //PrintKeysAndValues

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

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

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