System.Net.DnsPermissionAttribute Class

Summary

Specifies permission to request information from Domain Name Servers.

C# Syntax:

[AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Constructor | AttributeTargets.Method)] [Serializable] public sealed class DnsPermissionAttribute : CodeAccessSecurityAttribute

The security information declared by DnsPermissionAttribute is stored in the metadata of the attribute target, which is the class to which the DnsPermissionAttribute is applied. The system then accesses this information at run-time. The SecurityAction passed to the constructor determines the allowable DNS targets.

These security attributes are used only for the conceptual topic at MSDN: declarativesecurity. For the conceptual topic at MSDN: imperativesecurity, use the corresponding DnsPermission class.

Security access is either fully restricted, or fully unrestricted. Set the PermissionState.Unrestricted property to true to grant access, or false for no access. Set this property as a named parameter.

For more information about using attributes, see the conceptual topic at MSDN: extendingmetadatausingattributes.

The following example uses DnsPermissionAttribute to apply declarative security to a custom class.

//Uses the DnsPermissionAttribute to restrict access only to those who have permission.
[DnsPermission(SecurityAction.Demand, Unrestricted = true)]
public class MyClass{

public static IPAddress GetIPAddress(){
     IPAddress ipAddress = Dns.Resolve("localhost").AddressList[0];
     return ipAddress;
}
public static void Main(){
try{
     //Grants Access.
     Console.WriteLine(" Access granted\n The local host IP Address is :" + 
                                  MyClass.GetIPAddress().ToString());
}
// Denies Access.
catch(SecurityException securityException){
     Console.WriteLine("Access denied");	
     Console.WriteLine(securityException.ToString());
}

    

System.Net Namespace | CodeAccessSecurityAttribute

System.Net.DnsPermissionAttribute Member List:

Public Constructors

ctor #1

Initializes a new instance of the DnsPermissionAttribute class with the specified SecurityAction value.

Public Properties

Action (inherited from System.Security.Permissions.SecurityAttribute)	Read-write See base class member description: System.Security.Permissions.SecurityAttribute.Action Gets or sets a security action.
TypeId (inherited from System.Attribute)	Read-only See base class member description: System.Attribute.TypeId When implemented in a derived class, gets a unique identifier for this Attribute.
Unrestricted (inherited from System.Security.Permissions.SecurityAttribute)	Read-write See base class member description: System.Security.Permissions.SecurityAttribute.Unrestricted Gets or sets a value indicating whether full (unrestricted) permission to the resource protected by the attribute is declared.

Public Methods

CreatePermission	Overridden: Creates and returns a new instance of the DnsPermission class.
Equals (inherited from System.Object)	See base class member description: System.Object.Equals Derived from System.Object, the primary base class for all objects.
GetHashCode (inherited from System.Attribute)	See base class member description: System.Attribute.GetHashCode Returns the hash code for this instance.
GetType (inherited from System.Object)	See base class member description: System.Object.GetType Derived from System.Object, the primary base class for all objects.
IsDefaultAttribute (inherited from System.Attribute)	See base class member description: System.Attribute.IsDefaultAttribute When overridden in a derived class, returns an indication whether the value of this instance is the default value for the derived class.
Match (inherited from System.Attribute)	See base class member description: System.Attribute.Match When overridden in a derived class, returns a value indicating whether this instance equals a specified object.
ToString (inherited from System.Object)	See base class member description: System.Object.ToString Derived from System.Object, the primary base class for all objects.

Protected Methods

Finalize (inherited from System.Object)	See base class member description: System.Object.Finalize Derived from System.Object, the primary base class for all objects.
MemberwiseClone (inherited from System.Object)	See base class member description: System.Object.MemberwiseClone Derived from System.Object, the primary base class for all objects.

Hierarchy:

• System.Object
• System.Attribute
• System.Security.Permissions.SecurityAttribute
• System.Security.Permissions.CodeAccessSecurityAttribute
• System.Net.DnsPermissionAttribute

System.Net.DnsPermissionAttribute Member Details

Summary

Initializes a new instance of the DnsPermissionAttribute class with the specified SecurityAction value.

C# Syntax:

public DnsPermissionAttribute(    SecurityAction action );

action

One of the SecurityAction values.

Exceptions

Exception Type	Condition
ArgumentException	The action parameter is not a valid SecurityAction.

The SecurityAction value passed to this constructor specifies the allowable DnsPermissionAttribute targets.

The following example uses DnsPermissionAttribute to apply declarative security to a custom class.

//Uses the DnsPermissionAttribute to restrict access only to those who have permission.
[DnsPermission(SecurityAction.Demand, Unrestricted = true)]
public class MyClass{

public static IPAddress GetIPAddress(){
     IPAddress ipAddress = Dns.Resolve("localhost").AddressList[0];
     return ipAddress;
}
public static void Main(){
try{
     //Grants Access.
     Console.WriteLine(" Access granted\n The local host IP Address is :" + 
                                  MyClass.GetIPAddress().ToString());
}
// Denies Access.
catch(SecurityException securityException){
     Console.WriteLine("Access denied");	
     Console.WriteLine(securityException.ToString());
}

    

Return to top

Inherited
See base class member description: System.Security.Permissions.SecurityAttribute.Action

Summary

Gets or sets a security action.

C# Syntax:

public SecurityAction Action {get; set;}

This property is inherited by all classes implementing custom attributes for declarative security.

Return to top

Inherited
See base class member description: System.Attribute.TypeId

Summary

When implemented in a derived class, gets a unique identifier for this Attribute.

C# Syntax:

public virtual object TypeId {get;}

As implemented, this identifier is merely the Type of the attribute. However, it is intended that the unique identifier be used to identify two attributes of the same type.

Return to top

Inherited
See base class member description: System.Security.Permissions.SecurityAttribute.Unrestricted

Summary

Gets or sets a value indicating whether full (unrestricted) permission to the resource protected by the attribute is declared.

C# Syntax:

public bool Unrestricted {get; set;}

This property is inherited by all classes implementing custom attributes for declarative security.

Return to top

Summary

Creates and returns a new instance of the DnsPermission class.

C# Syntax:

public override IPermission CreatePermission();

Return Value:

A DnsPermission corresponding to the security declaration.

The CreatePermission method is called by the security system, not by application code. The security information described by DnsPermissionAttribute is stored in the metadata of the attribute target. which is the class to which DnsPermissionAttribute is applied. The system then accesses the information at run time and calls DnsPermissionAttribute.CreatePermission. The system uses the returned IPermission to enforce the specified security requirements.

Return to top

Inherited
See base class member description: System.Object.Equals

C# Syntax:

public virtual bool Equals(    object obj );

For more information on members inherited from System.Object click on the link above.

Return to top

Inherited
See base class member description: System.Object.Finalize

C# Syntax:

~DnsPermissionAttribute();

For more information on members inherited from System.Object click on the link above.

Return to top

Inherited
See base class member description: System.Attribute.GetHashCode

Summary

Returns the hash code for this instance.

C# Syntax:

public override int GetHashCode();

Return Value:

A 32-bit signed integer hash code.

Return to top

Inherited
See base class member description: System.Object.GetType

C# Syntax:

public Type GetType();

For more information on members inherited from System.Object click on the link above.

Return to top

Inherited
See base class member description: System.Attribute.IsDefaultAttribute

Summary

When overridden in a derived class, returns an indication whether the value of this instance is the default value for the derived class.

C# Syntax:

public virtual bool IsDefaultAttribute();

Return Value:

true if this instance is the default attribute for the class; otherwise, false.

The default implementation of this class returns false, and must be implemented in the derived class to be useful to that class.

The implementation of this method in a derived class compares the value of this instance to a standard, default value obtained by some means, then returns a Boolean value that indicates whether the value of this instance is equal to the standard. The standard value is typically coded as a constant in the implementation, or stored programmatically in a field used by the implementation.

Return to top

Inherited
See base class member description: System.Attribute.Match

Summary

When overridden in a derived class, returns a value indicating whether this instance equals a specified object.

C# Syntax:

public virtual bool Match(    object obj );

obj

An Object to compare with this instance of Attribute.

Return Value:

true if this instance equals obj; otherwise, false.

This method determines if one Attribute equals another. Its default implementation is the same as Attribute.Equals, which performs a value and reference comparison. Override this method to implement support for attribute values, such as flags or bitfields, that consist of components that are meaningful in themselves. For example, consider an attribute whose value is a binary field divided into a bitfield of flags. Two instances of this attribute have one flag in set in common while all the other flags differ. The Equal method cannot determine that the two instances have the same flag set, but the Match method can.

Return to top

Inherited
See base class member description: System.Object.MemberwiseClone

C# Syntax:

protected object MemberwiseClone();

For more information on members inherited from System.Object click on the link above.

Return to top

Inherited
See base class member description: System.Object.ToString

C# Syntax:

public virtual string ToString();

For more information on members inherited from System.Object click on the link above.

Return to top

Top of page