DispatcherFrame.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Base / System / Windows / Threading / DispatcherFrame.cs / 1 / DispatcherFrame.cs
                        

                        
                            using System; 
using System.Security;

namespace System.Windows.Threading
{ 
    /// 
    ///     Representation of Dispatcher frame. 
    ///  
    public class DispatcherFrame : DispatcherObject
    { 

        /// 
        ///     Critical: This code exists to ensure that the static variables initialized
        ///     do not cause security violations.The reason this comes into existance is because 
        ///     of the call to RegisterWindowMessage
        ///     TreatAsSafe:This is safe to call 
        ///  
        [SecurityCritical,SecurityTreatAsSafe]
        static DispatcherFrame() 
        {
        }

        ///  
        ///     Constructs a new instance of the DispatcherFrame class.
        ///  
        public DispatcherFrame() : this(true) 
        {
        } 

        /// 
        ///     Constructs a new instance of the DispatcherFrame class.
        ///  
        /// 
        ///     Indicates whether or not this frame will exit when all frames 
        ///     are requested to exit. 
        ///     

        ///     Dispatcher frames typically break down into two categories: 
        ///     1) Long running, general purpose frames, that exit only when
        ///        told to.  These frames should exit when requested.
        ///     2) Short running, very specific frames that exit themselves
        ///        when an important criteria is met.  These frames may 
        ///        consider not exiting when requested in favor of waiting
        ///        for their important criteria to be met.  These frames 
        ///        should have a timeout associated with them. 
        /// 
        public DispatcherFrame(bool exitWhenRequested) 
        {
            _exitWhenRequested = exitWhenRequested;
            _continue = true;
        } 

        /// 
 
        ///     Indicates that this dispatcher frame should exit. 
        /// 
        ///  
        ///     Critical - calls a critical method - postThreadMessage.
        ///     PublicOK - all we're doing is posting a current message to our thread.
        ///                net effect is the dispatcher "wakes up"
        ///                and uses the continue flag ( which may have just changed). 
        /// 
        public bool Continue 
        { 
            get
            { 
                // This method is free-threaded.

                // First check if this frame wants to continue.
                bool shouldContinue = _continue; 
                if(shouldContinue)
                { 
                    // This frame wants to continue, so next check if it will 
                    // respect the "exit requests" from the dispatcher.
                    if(_exitWhenRequested) 
                    {
                        Dispatcher dispatcher = Dispatcher;

                        // This frame is willing to respect the "exit requests" of 
                        // the dispatcher, so check them.
                        if(dispatcher._exitAllFrames || dispatcher._hasShutdownStarted) 
                        { 
                            shouldContinue = false;
                        } 
                    }
                }

                return shouldContinue; 
            }
 
            [SecurityCritical] 
            set
            { 
                // This method is free-threaded.

                _continue = value;
 
                // Post a message so that the message pump will wake up and
                // check our continue state. 
                Dispatcher.BeginInvoke(DispatcherPriority.Send, (DispatcherOperationCallback) delegate(object unused) {return null;}, null); 
            }
        } 

        private bool _exitWhenRequested;
        private bool _continue;
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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