EventHandlerService.cs source code in C# .NET

                        Code:
                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Designer / WinForms / System / WinForms / Design / EventHandlerService.cs / 1 / EventHandlerService.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

/* 
 */ 
namespace System.Windows.Forms.Design {
 
    using System.Diagnostics;
    using System;
    using System.Windows.Forms;
 
    /// 
    ///  
    ///  
    /// 
    public sealed class EventHandlerService : IEventHandlerService { 

        // We cache the last requested handler for speed.
        //
        private object  lastHandler; 
        private Type    lastHandlerType;
 
        // The handler stack 
        //
        private HandlerEntry handlerHead; 

        // Our change event
        //
        private EventHandler changedEvent; 

        private readonly Control focusWnd; 
 
        /// 
        ///  
        ///    [To be supplied.]
        /// 
        public EventHandlerService(Control focusWnd) {
            this.focusWnd = focusWnd; 
        }
 
 
        /// 
        ///  
        ///    [To be supplied.]
        /// 
        public event EventHandler EventHandlerChanged {
            add { 
                changedEvent += value;
            } 
            remove { 
                changedEvent -= value;
            } 
        }

        /// 
        ///  
        ///    [To be supplied.]
        ///  
        public Control FocusWindow { 
            get {
                return focusWnd; 
            }
        }

        ///  
        /// 
        ///     
        ///       Gets the currently active event handler of the specified type. 
        /// 
        public object GetHandler(Type handlerType) { 
            if (handlerType == lastHandlerType) {
                return lastHandler;
            }
 
            for (HandlerEntry entry = handlerHead; entry != null; entry = entry.next) {
                if (entry.handler != null && handlerType.IsInstanceOfType(entry.handler)) { 
                    lastHandlerType = handlerType; 
                    lastHandler = entry.handler;
                    return entry.handler; 
                }
            }
            return null;
        } 

        ///  
        ///  
        ///      Fires an OnEventHandlerChanged event.
        ///  
        private void OnEventHandlerChanged(EventArgs e) {
            if (changedEvent != null) {
                ((EventHandler)changedEvent)(this, e);
            } 
        }
 
        ///  
        /// 
        ///     
        ///       Pops
        ///       the given handler off of the stack.
        /// 
        public void PopHandler(object handler) { 
            for (HandlerEntry entry = handlerHead; entry != null; entry = entry.next) {
                if (entry.handler == handler) { 
                    handlerHead = entry.next; 
                    lastHandler = null;
                    lastHandlerType = null; 
                    OnEventHandlerChanged(EventArgs.Empty);
                    return;
                }
            } 

            Debug.Assert(handler == null || handlerHead == null, "Failed to locate handler to remove from list."); 
        } 

        ///  
        /// 
        ///    Pushes a new event handler on the stack.
        /// 
        public void PushHandler(object handler) { 
            handlerHead = new HandlerEntry(handler, handlerHead);
            // Update the handlerType if the Handler pushed is the same type as the last one .... 
            // This is true when SplitContainer is on the form and Edit Properties pushed another handler. 
            lastHandlerType = handler.GetType();
            lastHandler = handlerHead.handler; 
            OnEventHandlerChanged(EventArgs.Empty);
        }

        ///  
        /// 
        ///     Contains a single node of our handler stack.  We typically 
        ///     have very few handlers, and the handlers are long-living, so 
        ///     I just implemented this as a linked list.
        ///  
        private sealed class HandlerEntry {
            public object       handler;
            public HandlerEntry next;
 
            /// 
            ///  
            ///     Creates a new handler entry objet. 
            /// 
            public HandlerEntry(object handler, HandlerEntry next) { 
                this.handler = handler;
                this.next = next;
            }
        } 
    }
 
 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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EventHandlerService.cs source code in C# .NET

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