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The Labs \ Source Viewer \ SSCLI \ System.Runtime.Remoting.Contexts \ ContextAttribute

SSCLI
  1. // ==++==
  2. //
  3. //
  4. // Copyright (c) 2006 Microsoft Corporation. All rights reserved.
  5. //
  6. // The use and distribution terms for this software are contained in the file
  7. // named license.txt, which can be found in the root of this distribution.
  8. // By using this software in any fashion, you are agreeing to be bound by the
  9. // terms of this license.
  10. //
  11. // You must not remove this notice, or any other, from this software.
  12. //
  13. //
  14. // ==--==
  15. /*============================================================
  16. **
  17. ** File:    ContextProperty.cs
  18. **
  19. ** A contextProperty is a name-value pair holding the property
  20. ** name and the object representing the property in a context.
  21. ** An array of these is returned by Context::GetContextProperties()
  22. **
  23. **
  24. **
  25. ===========================================================*/
  27. namespace System.Runtime.Remoting.Contexts
  28. {
  29.    
  30.     using System;
  31.     using System.Threading;
  32.     using System.Reflection;
  33.     using System.Runtime.InteropServices;
  34.     using System.Runtime.Remoting.Activation;
  35.     using System.Security.Permissions;
  36.    
  37.     /// <internalonly/>
  38.     [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  39.     [SecurityPermissionAttribute(SecurityAction.InheritanceDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  40.     [System.Runtime.InteropServices.ComVisible(true)]
  41.     public class ContextProperty
  42.     {
  43.         internal string _name;
  44.         // property name
  45.         internal object _property;
  46.         // property object
  47.         /// <internalonly/>
  48.         public virtual string Name {
  49.             get { return _name; }
  50.         }
  51.        
  52.         /// <internalonly/>
  53.         public virtual object Property {
  54.             get { return _property; }
  55.         }
  56.        
  57. /* can't create outside the package */       
  58.         internal ContextProperty(string name, object prop)
  59.         {
  60.             _name = name;
  61.             _property = prop;
  62.         }
  63.     }
  64.    
  65.     // The IContextAttribute interface is implemented by attribute classes.
  66.     // The attributes contribute a property which resides in a context and
  67.     // enforces a specific policy for the objects created in that context.
  68.     /// <internalonly/>
  69.     [System.Runtime.InteropServices.ComVisible(true)]
  70.     public interface IContextAttribute
  71.     {
  72.         /// <internalonly/>
  73.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  74.         bool IsContextOK(Context ctx, IConstructionCallMessage msg);
  75.         /// <internalonly/>
  76.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  77.         void GetPropertiesForNewContext(IConstructionCallMessage msg);
  78.     }
  79.    
  80.     // This interface is exposed by the property contributed to a context
  81.     // by an attribute. By default, it is also implemented by the ContextAttribute
  82.     // base class which every attribute class must extend from.
  83.     /// <internalonly/>
  84.     [System.Runtime.InteropServices.ComVisible(true)]
  85.     public interface IContextProperty
  86.     {
  87.         /// <internalonly/>
  88.         // This is the name under which the property will be added
  89.         // to the {name,property} table in a context.
  90.         string Name {
  91.             [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  92.             get;
  93.         }
  94.         /// <internalonly/>
  95.         // After forming the newCtx, we ask each property if it is happy
  96.         // with the context. We expect most implementations to say yes.
  97.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  98.         bool IsNewContextOK(Context newCtx);
  99.         /// <internalonly/>
  100.        
  101.         // New method. All properties are notified when the context
  102.         // they are in is frozen.
  103.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  104.         void Freeze(Context newContext);
  105.     }
  106.    
  107.     /// <internalonly/>
  108.     [System.Runtime.InteropServices.ComVisible(true)]
  109.     public interface IContextPropertyActivator
  110.     {
  111.         /// <internalonly/>
  112.         // This method lets properties in the current context have a say in
  113.         // whether an activation may be done 'here' or not.
  114.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  115.         bool IsOKToActivate(IConstructionCallMessage msg);
  116.         /// <internalonly/>
  117.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  118.         void CollectFromClientContext(IConstructionCallMessage msg);
  119.         /// <internalonly/>
  120.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  121.         bool DeliverClientContextToServerContext(IConstructionCallMessage msg);
  122.         /// <internalonly/>
  123.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  124.         void CollectFromServerContext(IConstructionReturnMessage msg);
  125.         /// <internalonly/>
  126.         [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  127.         bool DeliverServerContextToClientContext(IConstructionReturnMessage msg);
  128.     }
  129.    
  130.    
  131.     // All context attribute classes must extend from this base class.
  132.     // This class provides the base implementations which the derived
  133.     // classes are free to over-ride. The base implementations provide
  134.     // the default answers to various questions.
  135.    
  136.     /// <internalonly/>
  137.     [AttributeUsage(AttributeTargets.Class), Serializable()]
  138.     [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  139.     [SecurityPermissionAttribute(SecurityAction.InheritanceDemand, Flags = SecurityPermissionFlag.Infrastructure)]
  140.     [System.Runtime.InteropServices.ComVisible(true)]
  141.     public class ContextAttribute : Attribute, IContextAttribute, IContextProperty
  142.     {
  143.         /// <internalonly/>
  144.         protected string AttributeName;
  145.        
  146.         // The derived class must call: base(name);
  147.         /// <internalonly/>
  148.         public ContextAttribute(string name)
  149.         {
  150.             AttributeName = name;
  151.         }
  152.        
  153.         // IContextPropery::Name
  154.         // Default implementation provides AttributeName as the property name.
  155.         /// <internalonly/>
  156.         public virtual string Name {
  157.             get { return AttributeName; }
  158.         }
  159.        
  160.         // IContextProperty::IsNewContextOK
  161.         /// <internalonly/>
  162.         public virtual bool IsNewContextOK(Context newCtx)
  163.         {
  164.             // This will be called before entering the newCtx
  165.             // Default implementation says OK.
  166.             return true;
  167.         }
  168.        
  169.         // IContextProperty::Freeze
  170.         // Default implementation does nothing
  171.         /// <internalonly/>
  172.         public virtual void Freeze(Context newContext)
  173.         {
  174.             BCLDebug.Log("ContextAttribute::ContextProperty::Freeze" + " for context " + newContext);
  175.         }
  176.        
  177.         // Object::Equals
  178.         // Default implementation just compares the names
  179.         /// <internalonly/>
  180.         public override bool Equals(object o)
  181.         {
  182.             IContextProperty prop = o as IContextProperty;
  183.             return (null != prop) && AttributeName.Equals(prop.Name);
  184.         }
  185.        
  186.         /// <internalonly/>
  187.         public override int GetHashCode()
  188.         {
  189.             return this.AttributeName.GetHashCode();
  190.         }
  191.        
  192.         // IContextAttribute::IsContextOK
  193.         // Default calls Object::Equals on the property and does not
  194.         // bother with the ctorMsg.
  195.         /// <internalonly/>
  196.         public virtual bool IsContextOK(Context ctx, IConstructionCallMessage ctorMsg)
  197.         {
  198.             if (ctx == null)
  199.                 throw new ArgumentNullException("ctx");
  200.             if (ctorMsg == null)
  201.                 throw new ArgumentNullException("ctorMsg");
  202.            
  203.             BCLDebug.Assert(ctorMsg.ActivationType.IsMarshalByRef, "Activation on a non MarshalByRef object");
  204.            
  205.             if (!ctorMsg.ActivationType.IsContextful) {
  206.                 return true;
  207.             }
  208.            
  209.             object prop = ctx.GetProperty(AttributeName);
  210.             if ((prop != null) && (Equals(prop))) {
  211.                 return true;
  212.             }
  213.             return false;
  214.         }
  215.        
  216.         // IContextAttribute::GetPropertiesForNewContext
  217.         // Default adds the attribute itself w/o regard to the current
  218.         // list of properties
  219.         /// <internalonly/>
  220.         public virtual void GetPropertiesForNewContext(IConstructionCallMessage ctorMsg)
  221.         {
  222.             if (ctorMsg == null)
  223.                 throw new ArgumentNullException("ctorMsg");
  224.             ctorMsg.ContextProperties.Add((IContextProperty)this);
  225.         }
  226.     }
  227.    
  228.    
  229. }

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