BackgroundWorker.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / CompMod / System / ComponentModel / BackgroundWorker.cs / 1 / BackgroundWorker.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

 
namespace System.ComponentModel 
{
    using System.ComponentModel.Design.Serialization; 
    using System.Diagnostics;
    using System.Security.Permissions;
    using System.Threading;
 
    [
        SRDescription(SR.BackgroundWorker_Desc), 
        DefaultEvent("DoWork"), 
        HostProtection(SharedState = true)
    ] 
    public class BackgroundWorker : Component
    {
        // Private statics
        private static readonly object doWorkKey = new object(); 
        private static readonly object runWorkerCompletedKey = new object();
        private static readonly object progressChangedKey = new object(); 
 
        // Private instance members
        private bool                                canCancelWorker = false; 
        private bool                                workerReportsProgress = false;
        private bool                                cancellationPending = false;
        private bool                                isRunning = false;
        private AsyncOperation                      asyncOperation = null; 
        private readonly WorkerThreadStartDelegate  threadStart;
        private readonly SendOrPostCallback operationCompleted; 
        private readonly SendOrPostCallback progressReporter; 

        public BackgroundWorker() 
        {
            threadStart        = new WorkerThreadStartDelegate(WorkerThreadStart);
            operationCompleted = new SendOrPostCallback(AsyncOperationCompleted);
            progressReporter   = new SendOrPostCallback(ProgressReporter); 
        }
 
        private void AsyncOperationCompleted(object arg) 
        {
            isRunning = false; 
            cancellationPending = false;
            OnRunWorkerCompleted((RunWorkerCompletedEventArgs)arg);
        }
 
        [
          Browsable(false), 
          SRDescription(SR.BackgroundWorker_CancellationPending) 
        ]
        public bool CancellationPending 
        {
            get { return cancellationPending; }
        }
 
        public void CancelAsync()
        { 
            if (!WorkerSupportsCancellation) 
            {
                throw new InvalidOperationException(SR.GetString(SR.BackgroundWorker_WorkerDoesntSupportCancellation)); 
            }

            cancellationPending = true;
        } 

        [ 
          SRCategory(SR.PropertyCategoryAsynchronous), 
          SRDescription(SR.BackgroundWorker_DoWork)
        ] 
        public event DoWorkEventHandler DoWork
        {
            add
            { 
                this.Events.AddHandler(doWorkKey, value);
            } 
            remove 
            {
                this.Events.RemoveHandler(doWorkKey, value); 
            }
        }

        ///  
        [
          Browsable(false), 
          SRDescription(SR.BackgroundWorker_IsBusy) 
        ]
        public bool IsBusy 
        {
            get
            {
                return isRunning; 
            }
        } 
 
        /// 
        protected virtual void OnDoWork(DoWorkEventArgs e) 
        {
            DoWorkEventHandler handler = (DoWorkEventHandler)(Events[doWorkKey]);
            if (handler != null)
            { 
                handler(this, e);
            } 
        } 

        ///  
        protected virtual void OnRunWorkerCompleted(RunWorkerCompletedEventArgs e)
        {
            RunWorkerCompletedEventHandler handler = (RunWorkerCompletedEventHandler)(Events[runWorkerCompletedKey]);
            if (handler != null) 
            {
                handler(this, e); 
            } 
        }
 
        protected virtual void OnProgressChanged(ProgressChangedEventArgs e)
        {
            ProgressChangedEventHandler handler = (ProgressChangedEventHandler)(Events[progressChangedKey]);
            if (handler != null) 
            {
                handler(this, e); 
            } 
        }
 
        [
          SRCategory(SR.PropertyCategoryAsynchronous),
          SRDescription(SR.BackgroundWorker_ProgressChanged)
        ] 
        public event ProgressChangedEventHandler ProgressChanged
        { 
            add 
            {
                this.Events.AddHandler(progressChangedKey, value); 
            }
            remove
            {
                this.Events.RemoveHandler(progressChangedKey, value); 
            }
        } 
 
        // Gets invoked through the AsyncOperation on the proper thread.
        private void ProgressReporter(object arg) 
        {
            OnProgressChanged((ProgressChangedEventArgs)arg);
        }
 
        // Cause progress update to be posted through current AsyncOperation.
        public void ReportProgress(int percentProgress) 
        { 
            ReportProgress(percentProgress, null);
        } 

        // Cause progress update to be posted through current AsyncOperation.
        public void ReportProgress(int percentProgress, object userState)
        { 
            if (!WorkerReportsProgress)
            { 
                throw new InvalidOperationException(SR.GetString(SR.BackgroundWorker_WorkerDoesntReportProgress)); 
            }
 
            ProgressChangedEventArgs args = new ProgressChangedEventArgs(percentProgress, userState);

            if (asyncOperation != null)
            { 
                asyncOperation.Post(progressReporter, args);
            } 
            else 
            {
                progressReporter(args); 
            }
        }

        public void RunWorkerAsync() 
        {
            RunWorkerAsync(null); 
        } 

        public void RunWorkerAsync(object argument) 
        {
            if (isRunning)
            {
                throw new InvalidOperationException(SR.GetString(SR.BackgroundWorker_WorkerAlreadyRunning)); 
            }
 
            isRunning = true; 
            cancellationPending = false;
 
            asyncOperation = AsyncOperationManager.CreateOperation(null);
            threadStart.BeginInvoke(argument,
                                    null,
                                    null); 
        }
 
        [ 
          SRCategory(SR.PropertyCategoryAsynchronous),
          SRDescription(SR.BackgroundWorker_RunWorkerCompleted) 
        ]
        public event RunWorkerCompletedEventHandler RunWorkerCompleted
        {
            add 
            {
                this.Events.AddHandler(runWorkerCompletedKey, value); 
            } 
            remove
            { 
                this.Events.RemoveHandler(runWorkerCompletedKey, value);
            }
        }
 
        [ SRCategory(SR.PropertyCategoryAsynchronous),
          SRDescription(SR.BackgroundWorker_WorkerReportsProgress), 
          DefaultValue(false) 
        ]
        public bool WorkerReportsProgress 
        {
            get { return workerReportsProgress; }
            set { workerReportsProgress = value; }
        } 

        [ 
          SRCategory(SR.PropertyCategoryAsynchronous), 
          SRDescription(SR.BackgroundWorker_WorkerSupportsCancellation),
          DefaultValue(false) 
        ]
        public bool WorkerSupportsCancellation
        {
            get { return canCancelWorker; } 
            set { canCancelWorker = value; }
        } 
 
        private delegate void WorkerThreadStartDelegate(object argument);
 
        private void WorkerThreadStart(object argument)
        {
            object workerResult = null;
            Exception error = null; 
            bool cancelled = false;
 
            try 
            {
                DoWorkEventArgs doWorkArgs = new DoWorkEventArgs(argument); 
                OnDoWork(doWorkArgs);
                if (doWorkArgs.Cancel)
                {
                    cancelled = true; 
                }
                else 
                { 
                    workerResult = doWorkArgs.Result;
                } 
            }
            catch (Exception exception)
            {
                error = exception; 
            }
 
            RunWorkerCompletedEventArgs e = 
                new RunWorkerCompletedEventArgs(workerResult, error, cancelled);
 
            asyncOperation.PostOperationCompleted(operationCompleted, e);
        }

    } 
}

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