httpapplicationstate.cs source code in C# .NET

                        Code:
                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / httpapplicationstate.cs / 1 / httpapplicationstate.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

/* 
 * Application State Dictionary class 
 *
 * Copyright (c) 1999 Microsoft Corporation 
 */

namespace System.Web {
    using System.Threading; 
    using System.Runtime.InteropServices;
    using System.Security.Permissions; 
 
    using System.Collections;
    using System.Collections.Specialized; 
    using System.Web;
    using System.Web.Util;

    // 
    //  Application state collection
    // 
 

    ///  
    ///    
    ///       The HttpApplicationState class enables developers to
    ///       share global information across multiple requests, sessions, and pipelines
    ///       within an ASP.NET application. (An ASP.NET application is the sum of all files, pages, 
    ///       handlers, modules, and code
    ///       within the scope of a virtual directory and its 
    ///       subdirectories on a single web server). 
    ///    
    ///  
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    public sealed class HttpApplicationState : NameObjectCollectionBase {
        // app lock with auto-unlock feature
        private HttpApplicationStateLock _lock = new HttpApplicationStateLock(); 

        // static object collections 
        private HttpStaticObjectsCollection _applicationStaticObjects; 
        private HttpStaticObjectsCollection _sessionStaticObjects;
 
        internal HttpApplicationState() : this(null, null) {
        }

        internal HttpApplicationState(HttpStaticObjectsCollection applicationStaticObjects, 
                                      HttpStaticObjectsCollection sessionStaticObjects)
            : base(Misc.CaseInsensitiveInvariantKeyComparer) { 
            _applicationStaticObjects = applicationStaticObjects; 

            if (_applicationStaticObjects == null) 
                _applicationStaticObjects = new HttpStaticObjectsCollection();

            _sessionStaticObjects = sessionStaticObjects;
 
            if (_sessionStaticObjects == null)
                _sessionStaticObjects = new HttpStaticObjectsCollection(); 
        } 

        // 
        // Internal accessor to session static objects collection
        //

        internal HttpStaticObjectsCollection SessionStaticObjects { 
            get { return _sessionStaticObjects;}
        } 
 
        //
        // Implementation of standard collection stuff 
        //


        ///  
        ///    Gets
        ///       the number of item objects in the application state collection. 
        ///  
        public override int Count {
            get { 
                int c = 0;
                _lock.AcquireRead();
                try {
                    c = base.Count; 
                }
                finally { 
                    _lock.ReleaseRead(); 
                }
 
                return c;
            }
        }
 
        // modifying methods
 
 
        /// 
        ///     
        ///       Adds
        ///       a new state object to the application state collection.
        ///    
        ///  
        public void Add(String name, Object value) {
            _lock.AcquireWrite(); 
            try { 
                BaseAdd(name, value);
            } 
            finally {
                _lock.ReleaseWrite();
            }
        } 

 
        ///  
        ///    Updates an HttpApplicationState value within the collection.
        ///  
        public void Set(String name, Object value) {
            _lock.AcquireWrite();
            try {
                BaseSet(name, value); 
            }
            finally { 
                _lock.ReleaseWrite(); 
            }
        } 


        /// 
        ///    Removes 
        ///       an
        ///       object from the application state collection by name. 
        ///  
        public void Remove(String name) {
            _lock.AcquireWrite(); 
            try {
                BaseRemove(name);
            }
            finally { 
                _lock.ReleaseWrite();
            } 
        } 

 
        /// 
        ///    Removes
        ///       an
        ///       object from the application state collection by name. 
        /// 
        public void RemoveAt(int index) { 
            _lock.AcquireWrite(); 
            try {
                BaseRemoveAt(index); 
            }
            finally {
                _lock.ReleaseWrite();
            } 
        }
 
 
        /// 
        ///     
        ///       Removes
        ///       all objects from the application state collection.
        ///    
        ///  
        public void Clear() {
            _lock.AcquireWrite(); 
            try { 
                BaseClear();
            } 
            finally {
                _lock.ReleaseWrite();
            }
        } 

 
        ///  
        ///    
        ///       Removes 
        ///       all objects from the application state collection.
        ///    
        /// 
        public void RemoveAll() { 
            Clear();
        } 
 
        // access by key
 

        /// 
        ///    
        ///       Enables user to retrieve application state object by name. 
        ///    
        ///  
        public Object Get(String name) { 
            Object obj = null;
            _lock.AcquireRead(); 
            try {
                obj = BaseGet(name);
            }
            finally { 
                _lock.ReleaseRead();
            } 
 
            return obj;
        } 


        /// 
        ///    Enables 
        ///       a user to add/remove/update a single application state object.
        ///  
        public Object this[String name] 
        {
            get { return Get(name);} 
            set { Set(name, value);}
        }

        // access by index 

 
        ///  
        ///    
        ///       Enables user 
        ///       to retrieve a single application state object by index.
        ///    
        /// 
        public Object Get(int index) { 
            Object obj = null;
 
            _lock.AcquireRead(); 
            try {
                obj = BaseGet(index); 
            }
            finally {
                _lock.ReleaseRead();
            } 

            return obj; 
        } 

 
        /// 
        ///    
        ///       Enables user to retrieve an application state object name by index.
        ///     
        /// 
        public String GetKey(int index) { 
            String s = null; 
            _lock.AcquireRead();
            try { 
                s = BaseGetKey(index);
            }
            finally {
                _lock.ReleaseRead(); 
            }
 
            return s; 
        }
 

        /// 
        ///    
        ///       Enables 
        ///       user to retrieve an application state object by index.
        ///     
        ///  
        public Object this[int index]
        { 
            get { return Get(index);}
        }

        // access to keys and values as arrays 

 
        ///  
        ///    
        ///       Enables user 
        ///       to retrieve all application state object names in collection.
        ///    
        /// 
        public String[] AllKeys { 
            get {
                String [] allKeys = null; 
 
                _lock.AcquireRead();
                try { 
                    allKeys = BaseGetAllKeys();
                }
                finally {
                    _lock.ReleaseRead(); 
                }
 
                return allKeys; 
            }
        } 

        //
        // Public properties
        // 

 
        ///  
        ///    
        ///       Returns "this". Provided for legacy ASP compatibility. 
        ///    
        /// 
        public HttpApplicationState Contents {
            get { return this;} 
        }
 
 
        /// 
        ///     
        ///       Exposes all objects declared via an <object
        ///       runat=server></object> tag within the ASP.NET application file.
        ///    
        ///  
        public HttpStaticObjectsCollection StaticObjects {
            get { return _applicationStaticObjects;} 
        } 

        // 
        //  Locking support
        //

 
        /// 
        ///     
        ///       Locks 
        ///       access to all application state variables. Facilitates access
        ///       synchronization. 
        ///    
        /// 
        public void Lock() {
            _lock.AcquireWrite(); 
        }
 
 
        /// 
        ///     
        ///       Unocks access to all application state variables. Facilitates access
        ///       synchronization.
        ///    
        ///  
        public void UnLock() {
            _lock.ReleaseWrite(); 
        } 

        internal void EnsureUnLock() { 
            _lock.EnsureReleaseWrite();
        }
    }
 

    // 
    //  Recursive read-write lock that allows removing of all 
    //  outstanding write locks from the current thread at once
    // 
    internal class HttpApplicationStateLock : ReadWriteObjectLock {
        private int _recursionCount;
        private int _threadId;
 
        internal HttpApplicationStateLock() {
        } 
 
        internal override void AcquireRead() {
            int currentThreadId = SafeNativeMethods.GetCurrentThreadId(); 

            if (_threadId != currentThreadId)
                base.AcquireRead();  // only if no write lock
        } 

        internal override void ReleaseRead() { 
            int currentThreadId = SafeNativeMethods.GetCurrentThreadId(); 

            if (_threadId != currentThreadId) 
                base.ReleaseRead();  // only if no write lock
        }

        internal override void AcquireWrite() { 
            int currentThreadId = SafeNativeMethods.GetCurrentThreadId();
 
            if (_threadId == currentThreadId) { 
                _recursionCount++;
            } 
            else {
                base.AcquireWrite();
                _threadId = currentThreadId;
                _recursionCount = 1; 
            }
        } 
 
        internal override void ReleaseWrite() {
            int currentThreadId = SafeNativeMethods.GetCurrentThreadId(); 

            if (_threadId == currentThreadId) {
                if (--_recursionCount == 0) {
                    _threadId = 0; 
                    base.ReleaseWrite();
                } 
            } 
        }
 
        //
        // release all write locks held by the current thread
        //
 
        internal void EnsureReleaseWrite() {
            int currentThreadId = SafeNativeMethods.GetCurrentThreadId(); 
 
            if (_threadId == currentThreadId) {
                _threadId = 0; 
                _recursionCount = 0;
                base.ReleaseWrite();
            }
        } 
    }
 
}
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