451 lines
15 KiB
C#
451 lines
15 KiB
C#
/*
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** 2015 October 7
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains C# code to download a single file based on a URI.
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*/
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using System;
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using System.ComponentModel;
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using System.Diagnostics;
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using System.IO;
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using System.Net;
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using System.Reflection;
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using System.Runtime.InteropServices;
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using System.Threading;
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///////////////////////////////////////////////////////////////////////////////
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#region Assembly Metadata
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[assembly: AssemblyTitle("GetFile Tool")]
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[assembly: AssemblyDescription("Download a single file based on a URI.")]
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[assembly: AssemblyCompany("SQLite Development Team")]
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[assembly: AssemblyProduct("SQLite")]
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[assembly: AssemblyCopyright("Public Domain")]
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[assembly: ComVisible(false)]
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[assembly: Guid("5c4b3728-1693-4a33-a218-8e6973ca15a6")]
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[assembly: AssemblyVersion("1.0.*")]
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#if DEBUG
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[assembly: AssemblyConfiguration("Debug")]
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#else
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[assembly: AssemblyConfiguration("Release")]
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#endif
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#endregion
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///////////////////////////////////////////////////////////////////////////////
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namespace GetFile
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{
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/// <summary>
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/// This enumeration is used to represent all the possible exit codes from
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/// this tool.
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/// </summary>
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internal enum ExitCode
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{
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/// <summary>
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/// The file download was a success.
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/// </summary>
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Success = 0,
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/// <summary>
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/// The command line arguments are missing (i.e. null). Generally,
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/// this should not happen.
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/// </summary>
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MissingArgs = 1,
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/// <summary>
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/// The wrong number of command line arguments was supplied.
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/// </summary>
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WrongNumArgs = 2,
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/// <summary>
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/// The URI specified on the command line could not be parsed as a
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/// supported absolute URI.
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/// </summary>
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BadUri = 3,
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/// <summary>
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/// The file name portion of the URI specified on the command line
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/// could not be extracted from it.
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/// </summary>
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BadFileName = 4,
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/// <summary>
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/// The temporary directory is either invalid (i.e. null) or does not
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/// represent an available directory.
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/// </summary>
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BadTempPath = 5,
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/// <summary>
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/// An exception was caught in <see cref="Main" />. Generally, this
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/// should not happen.
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/// </summary>
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Exception = 6,
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/// <summary>
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/// The file download was canceled. This tool does not make use of
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/// the <see cref="WebClient.CancelAsync" /> method; therefore, this
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/// should not happen.
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/// </summary>
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DownloadCanceled = 7,
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/// <summary>
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/// The file download encountered an error. Further information about
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/// this error should be displayed on the console.
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/// </summary>
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DownloadError = 8
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}
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///////////////////////////////////////////////////////////////////////////
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internal static class Program
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{
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#region Private Data
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/// <summary>
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/// This is used to synchronize multithreaded access to the
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/// <see cref="previousPercent" /> and <see cref="exitCode"/>
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/// fields.
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/// </summary>
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private static readonly object syncRoot = new object();
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///////////////////////////////////////////////////////////////////////
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/// <summary>
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/// This event will be signed when the file download has completed,
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/// even if the file download itself was canceled or unsuccessful.
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/// </summary>
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private static EventWaitHandle doneEvent;
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///////////////////////////////////////////////////////////////////////
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/// <summary>
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/// The previous file download completion percentage seen by the
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/// <see cref="DownloadProgressChanged" /> event handler. This value
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/// is never decreased, nor is it ever reset to zero.
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/// </summary>
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private static int previousPercent = 0;
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///////////////////////////////////////////////////////////////////////
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/// <summary>
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/// This will be the exit code returned by this tool after the file
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/// download completes, successfully or otherwise. This value is only
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/// changed by the <see cref="DownloadFileCompleted" /> event handler.
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/// </summary>
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private static ExitCode exitCode = ExitCode.Success;
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#endregion
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///////////////////////////////////////////////////////////////////////
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#region Private Support Methods
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/// <summary>
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/// This method displays an error message to the console and/or
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/// displays the command line usage information for this tool.
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/// </summary>
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/// <param name="message">
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/// The error message to display, if any.
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/// </param>
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/// <param name="usage">
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/// Non-zero to display the command line usage information.
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/// </param>
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private static void Error(
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string message,
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bool usage
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)
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{
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if (message != null)
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Console.WriteLine(message);
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string fileName = Path.GetFileName(
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Process.GetCurrentProcess().MainModule.FileName);
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Console.WriteLine(String.Format("usage: {0} <uri>", fileName));
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}
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///////////////////////////////////////////////////////////////////////
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/// <summary>
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/// This method attempts to determine the file name portion of the
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/// specified URI.
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/// </summary>
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/// <param name="uri">
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/// The URI to process.
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/// </param>
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/// <returns>
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/// The file name portion of the specified URI -OR- null if it cannot
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/// be determined.
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/// </returns>
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private static string GetFileName(
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Uri uri
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)
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{
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if (uri == null)
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return null;
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string pathAndQuery = uri.PathAndQuery;
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if (String.IsNullOrEmpty(pathAndQuery))
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return null;
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int index = pathAndQuery.LastIndexOf('/');
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if ((index < 0) || (index == pathAndQuery.Length))
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return null;
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return pathAndQuery.Substring(index + 1);
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}
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#endregion
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///////////////////////////////////////////////////////////////////////
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#region Private Event Handlers
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/// <summary>
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/// This method is an event handler that is called when the file
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/// download completion percentage changes. It will display progress
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/// on the console. Special care is taken to make sure that progress
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/// events are not displayed out-of-order, even if duplicate and/or
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/// out-of-order events are received.
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/// </summary>
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/// <param name="sender">
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/// The source of the event.
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/// </param>
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/// <param name="e">
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/// Information for the event being processed.
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/// </param>
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private static void DownloadProgressChanged(
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object sender,
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DownloadProgressChangedEventArgs e
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)
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{
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if (e != null)
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{
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int percent = e.ProgressPercentage;
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lock (syncRoot)
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{
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if (percent > previousPercent)
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{
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Console.Write('.');
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if ((percent % 10) == 0)
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Console.Write(" {0}% ", percent);
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previousPercent = percent;
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}
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}
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}
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}
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///////////////////////////////////////////////////////////////////////
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/// <summary>
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/// This method is an event handler that is called when the file
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/// download has completed, successfully or otherwise. It will
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/// display the overall result of the file download on the console,
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/// including any <see cref="Exception" /> information, if applicable.
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/// The <see cref="exitCode" /> field is changed by this method to
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/// indicate the overall result of the file download and the event
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/// within the <see cref="doneEvent" /> field will be signaled.
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/// </summary>
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/// <param name="sender">
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/// The source of the event.
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/// </param>
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/// <param name="e">
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/// Information for the event being processed.
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/// </param>
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private static void DownloadFileCompleted(
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object sender,
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AsyncCompletedEventArgs e
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)
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{
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if (e != null)
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{
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lock (syncRoot)
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{
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if (previousPercent < 100)
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Console.Write(' ');
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}
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if (e.Cancelled)
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{
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Console.WriteLine("Canceled");
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lock (syncRoot)
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{
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exitCode = ExitCode.DownloadCanceled;
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}
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}
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else
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{
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Exception error = e.Error;
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if (error != null)
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{
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Console.WriteLine("Error: {0}", error);
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lock (syncRoot)
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{
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exitCode = ExitCode.DownloadError;
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}
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}
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else
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{
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Console.WriteLine("Done");
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}
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}
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}
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if (doneEvent != null)
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doneEvent.Set();
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}
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#endregion
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///////////////////////////////////////////////////////////////////////
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#region Program Entry Point
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/// <summary>
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/// This is the entry-point for this tool. It handles processing the
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/// command line arguments, setting up the web client, downloading the
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/// file, and saving it to the file system.
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/// </summary>
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/// <param name="args">
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/// The command line arguments.
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/// </param>
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/// <returns>
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/// Zero upon success; non-zero on failure. This will be one of the
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/// values from the <see cref="ExitCode" /> enumeration.
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/// </returns>
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private static int Main(
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string[] args
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)
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{
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//
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// NOTE: Sanity check the command line arguments.
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//
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if (args == null)
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{
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Error(null, true);
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return (int)ExitCode.MissingArgs;
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}
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if (args.Length != 1)
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{
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Error(null, true);
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return (int)ExitCode.WrongNumArgs;
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}
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//
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// NOTE: Attempt to convert the first (and only) command line
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// argument to an absolute URI.
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//
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Uri uri;
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if (!Uri.TryCreate(args[0], UriKind.Absolute, out uri))
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{
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Error("Could not create absolute URI from argument.", false);
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return (int)ExitCode.BadUri;
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}
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//
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// NOTE: Attempt to extract the file name portion of the URI we
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// just created.
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//
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string fileName = GetFileName(uri);
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if (fileName == null)
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{
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Error("Could not extract the file name from the URI.", false);
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return (int)ExitCode.BadFileName;
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}
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//
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// NOTE: Grab the temporary path setup for this process. If it is
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// unavailable, we will not continue.
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//
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string directory = Path.GetTempPath();
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if (String.IsNullOrEmpty(directory) ||
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!Directory.Exists(directory))
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{
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Error("Temporary directory is invalid or unavailable.", false);
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return (int)ExitCode.BadTempPath;
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}
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try
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{
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using (WebClient webClient = new WebClient())
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{
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//
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// NOTE: Create the event used to signal completion of the
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// file download.
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//
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doneEvent = new ManualResetEvent(false);
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//
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// NOTE: Hookup the event handlers we care about on the web
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// client. These are necessary because the file is
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// downloaded asynchronously.
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//
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webClient.DownloadProgressChanged +=
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new DownloadProgressChangedEventHandler(
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DownloadProgressChanged);
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webClient.DownloadFileCompleted +=
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new AsyncCompletedEventHandler(
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DownloadFileCompleted);
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//
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// NOTE: Build the fully qualified path and file name,
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// within the temporary directory, where the file to
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// be downloaded will be saved.
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//
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fileName = Path.Combine(directory, fileName);
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//
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// NOTE: If the file name already exists (in the temporary)
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// directory, delete it.
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//
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// TODO: Perhaps an error should be raised here instead?
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//
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if (File.Exists(fileName))
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File.Delete(fileName);
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//
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// NOTE: After kicking off the asynchronous file download
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// process, wait [forever] until the "done" event is
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// signaled.
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//
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Console.WriteLine(
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"Downloading \"{0}\" to \"{1}\"...", uri, fileName);
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webClient.DownloadFileAsync(uri, fileName);
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doneEvent.WaitOne();
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}
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lock (syncRoot)
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{
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return (int)exitCode;
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}
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}
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catch (Exception e)
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{
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//
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// NOTE: An exception was caught. Report it via the console
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// and return failure.
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//
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Error(e.ToString(), false);
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return (int)ExitCode.Exception;
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}
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}
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#endregion
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}
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}
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