/V4/PrismLibrary/Silverlight/Prism/Modularity/FileDownloader.cs

//===================================================================================

// Microsoft patterns & practices

// Composite Application Guidance for Windows Presentation Foundation and Silverlight

//===================================================================================

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

// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY

// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT

// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

// FITNESS FOR A PARTICULAR PURPOSE.

//===================================================================================

// The example companies, organizations, products, domain names,

// e-mail addresses, logos, people, places, and events depicted

// herein are fictitious.  No association with any real company,

// organization, product, domain name, email address, logo, person,

// places, or events is intended or should be inferred.

//===================================================================================

using System;

using System.Net;



namespace Microsoft.Practices.Prism.Modularity

{

    /// <summary>

    /// Defines the component used to download files.

    /// </summary>

    /// <remarks>This is mainly a wrapper for the <see cref="WebClient"/> class that implements <see cref="IFileDownloader"/>.</remarks>

    public class FileDownloader : IFileDownloader

    {

        private readonly WebClient webClient = new WebClient();



        private event EventHandler<DownloadProgressChangedEventArgs> _downloadProgressChanged;

        private event EventHandler<DownloadCompletedEventArgs> _downloadCompleted;



        /// <summary>

        /// Raised whenever the download progress changes.

        /// </summary>

        public event EventHandler<DownloadProgressChangedEventArgs> DownloadProgressChanged

        {

            add

            {

                if (this._downloadProgressChanged == null)

                {

                    this.webClient.DownloadProgressChanged += this.WebClient_DownloadProgressChanged;

                }



                this._downloadProgressChanged += value;

            }



            remove

            {

                this._downloadProgressChanged -= value;

                if (this._downloadProgressChanged == null)

                {

                    this.webClient.DownloadProgressChanged -= this.WebClient_DownloadProgressChanged;

                }

            }

        }





        /// <summary>

        /// Raised download is complete.

        /// </summary>

        public event EventHandler<DownloadCompletedEventArgs> DownloadCompleted

        {

            add

            {

                if (this._downloadCompleted == null)

                {                    

                    this.webClient.OpenReadCompleted += this.WebClient_OpenReadCompleted;

                }

                

                this._downloadCompleted += value;

            }



            remove

            {

                this._downloadCompleted -= value;

                if (this._downloadCompleted == null)

                {

                    this.webClient.OpenReadCompleted -= this.WebClient_OpenReadCompleted;

                }

            }

        }                



        /// <summary>

        /// Starts downloading asynchronously a file from <paramref name="uri"/>.

        /// </summary>

        /// <param name="uri">The location of the file to be downloaded.</param>

        /// <param name="userToken">Provides a user-specified identifier for the asynchronous task.</param>

        public void DownloadAsync(Uri uri, object userToken)

        {

            this.webClient.OpenReadAsync(uri, userToken);

        }



        private static DownloadCompletedEventArgs ConvertArgs(OpenReadCompletedEventArgs args)

        {            

            return new DownloadCompletedEventArgs(args.Error == null ? args.Result : null, args.Error, args.Cancelled, args.UserState);

        }



        void WebClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)

        {

            this._downloadProgressChanged(this, e);

        }



        private void WebClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)

        {

            this._downloadCompleted(this, ConvertArgs(e));

        }

    }

}