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[Microsoft.Android.Build.BaseTasks] retry when copying files (#245)
Context: dotnet/android#9133 Context: https://learn.microsoft.com/visualstudio/msbuild/copy-task?view=vs-2022 We sometimes get collisions between the Design-Time-Build (or AntiVirus) and our main build. This can result in errors such as: Error (active) XALNS7019 System.UnauthorizedAccessException: Access to the path 'D:\Projects\MauiApp2\obj\Debug\net9.0-android\android\assets\armeabi-v7a\MauiApp2.dll' is denied. at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.File.InternalDelete(String path, Boolean checkHost) at Microsoft.Android.Build.Tasks.Files.CopyIfChanged(String source, String destination) in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/Files.cs:line 125 at Xamarin.Android.Tasks.MonoAndroidHelper.CopyAssemblyAndSymbols(String source, String destination) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Utilities/MonoAndroidHelper.cs:line 344 at Xamarin.Android.Tasks.LinkAssembliesNoShrink.CopyIfChanged(ITaskItem source, ITaskItem destination) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/LinkAssembliesNoShrink.cs:line 161 at Xamarin.Android.Tasks.LinkAssembliesNoShrink.RunTask() in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/LinkAssembliesNoShrink.cs:line 76 at Microsoft.Android.Build.Tasks.AndroidTask.Execute() in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/AndroidTask.cs:line 25 MauiApp2 (net9.0-android) C:\Program Files\dotnet\packs\Microsoft.Android.Sdk.Windows\34.99.0-preview.6.340\tools\Xamarin.Android.Common.targets 1407 If we look at the [MSBuild `<Copy/>` task][0] we see that it has a retry system in the cases of `UnauthorizedAccessException` or `IOException` when the code is `ACCESS_DENIED` or `ERROR_SHARING_VIOLATION`. The `<Copy/>` task also has public `Retries` and `RetryDelayMilliseconds` properties to control behavior. Duplicate that kind of logic into our `Files.Copy*IfChanged()` helper methods. This should give our builds a bit more resiliency to these kinds of issues. Instead of adding new `Files.Copy*IfChanged()` method overloads which accept "retries" and "retryDelay" parameters, we instead use environment variables to allow overriding these values: * `DOTNET_ANDROID_FILE_WRITE_RETRY_ATTEMPTS`: The number of times to try to retry a copy operation; corresponds to the `Copy.Retries` MSBuild task property. The default value is 10. * `DOTNET_ANDROID_FILE_WRITE_RETRY_DELAY_MS`: The amount of time, in milliseconds, to delay between attempted copies; corresponds to the `Copy.RetryDelayMilliseconds` MSBuild task property. The default value is 1000 ms. [0]: https://github.com/dotnet/msbuild/blob/main/src/Tasks/Copy.cs#L897
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‎src/Microsoft.Android.Build.BaseTasks/Files.cs

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Original file line numberDiff line numberDiff line change
@@ -9,11 +9,25 @@
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using System.Text;
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using Xamarin.Tools.Zip;
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using Microsoft.Build.Utilities;
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using System.Threading;
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using System.Reflection.Metadata;
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using System.Runtime.InteropServices;
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using System.Collections;
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namespace Microsoft.Android.Build.Tasks
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{
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public static class Files
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{
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const int ERROR_ACCESS_DENIED = -2147024891;
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const int ERROR_SHARING_VIOLATION = -2147024864;
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const int DEFAULT_FILE_WRITE_RETRY_ATTEMPTS = 10;
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const int DEFAULT_FILE_WRITE_RETRY_DELAY_MS = 1000;
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static int fileWriteRetry = -1;
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static int fileWriteRetryDelay = -1;
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/// <summary>
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/// Windows has a MAX_PATH limit of 260 characters
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/// See: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#maximum-path-length-limitation
@@ -28,6 +42,37 @@ public static class Files
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public static readonly Encoding UTF8withoutBOM = new UTF8Encoding (encoderShouldEmitUTF8Identifier: false);
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readonly static byte[] Utf8Preamble = Encoding.UTF8.GetPreamble ();
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/// <summary>
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/// Checks for the environment variable DOTNET_ANDROID_FILE_WRITE_RETRY_ATTEMPTS to
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/// see if a custom value for the number of times to retry writing a file has been
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/// set.
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/// </summary>
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/// <returns>The value of DOTNET_ANDROID_FILE_WRITE_RETRY_ATTEMPTS or the default of DEFAULT_FILE_WRITE_RETRY_ATTEMPTS</returns>
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public static int GetFileWriteRetryAttempts ()
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{
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if (fileWriteRetry == -1) {
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var retryVariable = Environment.GetEnvironmentVariable ("DOTNET_ANDROID_FILE_WRITE_RETRY_ATTEMPTS");
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if (string.IsNullOrEmpty (retryVariable) || !int.TryParse (retryVariable, out fileWriteRetry))
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fileWriteRetry = DEFAULT_FILE_WRITE_RETRY_ATTEMPTS;
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}
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return fileWriteRetry;
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}
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/// <summary>
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/// Checks for the environment variable DOTNET_ANDROID_FILE_WRITE_RETRY_DELAY_MS to
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/// see if a custom value for the delay between trying to write a file has been
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/// set.
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/// </summary>
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/// <returns>The value of DOTNET_ANDROID_FILE_WRITE_RETRY_DELAY_MS or the default of DEFAULT_FILE_WRITE_RETRY_DELAY_MS</returns>
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public static int GetFileWriteRetryDelay ()
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{
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if (fileWriteRetryDelay == -1) {
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var delayVariable = Environment.GetEnvironmentVariable ("DOTNET_ANDROID_FILE_WRITE_RETRY_DELAY_MS");
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if (string.IsNullOrEmpty (delayVariable) || !int.TryParse (delayVariable, out fileWriteRetryDelay))
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fileWriteRetryDelay = DEFAULT_FILE_WRITE_RETRY_DELAY_MS;
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}
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return fileWriteRetryDelay;
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}
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/// <summary>
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/// Converts a full path to a \\?\ prefixed path that works on all Windows machines when over 260 characters
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/// NOTE: requires a *full path*, use sparingly
@@ -111,6 +156,33 @@ public static bool ArchiveZip (string target, Action<string> archiver)
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}
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public static bool CopyIfChanged (string source, string destination)
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{
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int retryCount = 0;
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int attempts = GetFileWriteRetryAttempts ();
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int delay = GetFileWriteRetryDelay ();
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while (retryCount <= attempts) {
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try {
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return CopyIfChangedOnce (source, destination);
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} catch (Exception e) {
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switch (e) {
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case UnauthorizedAccessException:
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case IOException:
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int code = Marshal.GetHRForException (e);
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if ((code != ERROR_ACCESS_DENIED && code != ERROR_SHARING_VIOLATION) || retryCount == attempts) {
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throw;
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};
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break;
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default:
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throw;
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}
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}
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retryCount++;
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Thread.Sleep (delay);
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}
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return false;
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}
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public static bool CopyIfChangedOnce (string source, string destination)
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{
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if (HasFileChanged (source, destination)) {
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var directory = Path.GetDirectoryName (destination);
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}
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public static bool CopyIfStreamChanged (Stream stream, string destination)
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{
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int retryCount = 0;
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int attempts = GetFileWriteRetryAttempts ();
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int delay = GetFileWriteRetryDelay ();
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while (retryCount <= attempts) {
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try {
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return CopyIfStreamChangedOnce (stream, destination);
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} catch (Exception e) {
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switch (e) {
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case UnauthorizedAccessException:
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case IOException:
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int code = Marshal.GetHRForException (e);
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if ((code != ERROR_ACCESS_DENIED && code != ERROR_SHARING_VIOLATION) || retryCount >= attempts) {
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throw;
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};
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break;
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default:
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throw;
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}
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}
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retryCount++;
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Thread.Sleep (delay);
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}
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return false;
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}
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public static bool CopyIfStreamChangedOnce (Stream stream, string destination)
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{
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if (HasStreamChanged (stream, destination)) {
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var directory = Path.GetDirectoryName (destination);

‎src/Microsoft.Android.Build.BaseTasks/Microsoft.Android.Build.BaseTasks.csproj

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<SignAssembly>true</SignAssembly>
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<AssemblyOriginatorKeyFile>..\..\product.snk</AssemblyOriginatorKeyFile>
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<AssemblyName>$(VendorPrefix)Microsoft.Android.Build.BaseTasks$(VendorSuffix)</AssemblyName>
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<LangVersion>12.0</LangVersion>
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</PropertyGroup>
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<ItemGroup>

‎tests/Microsoft.Android.Build.BaseTasks-Tests/FilesTests.cs

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using System.IO;
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using System.Runtime.InteropServices;
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using System.Text;
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using System.Threading;
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using System.Threading.Tasks;
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using Xamarin.Tools.Zip;
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using Microsoft.Android.Build.Tasks;
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}
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}
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[Test]
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public async Task CopyIfChanged_LockedFile ()
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{
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var dest = NewFile (contents: "foo", fileName: "foo_locked");
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var src = NewFile (contents: "foo0", fileName: "foo");
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using (var file = File.OpenWrite (dest)) {
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Assert.Throws<IOException> (() => Files.CopyIfChanged (src, dest));
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}
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src = NewFile (contents: "foo1", fileName: "foo");
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Assert.IsTrue (Files.CopyIfChanged (src, dest));
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src = NewFile (contents: "foo2", fileName: "foo");
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dest = NewFile (contents: "foo", fileName: "foo_locked2");
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var ev = new ManualResetEvent (false);
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var task = Task.Run (async () => {
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var file = File.Open (dest, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read);
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try {
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ev.Set ();
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await Task.Delay (2500);
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} finally {
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file.Close();
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file.Dispose ();
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}
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});
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ev.WaitOne ();
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Assert.IsTrue (Files.CopyIfChanged (src, dest));
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await task;
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}
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[Test]
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public void ExtractAll ()
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{

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