Fix progress timing for PutObject_Test9 test (fixes #1078)

Docs/API.md

@@ -1874,6 +1874,7 @@ try
     var ssec = new SSEC(aesEncryption.Key);
     var progress = new Progress<ProgressReport>(progressReport =>
     {
+        // Progress events are delivered asynchronously (see remark below)
         Console.WriteLine(
                 $"Percentage: {progressReport.Percentage}% TotalBytesTransferred: {progressReport.TotalBytesTransferred} bytes");
         if (progressReport.Percentage != 100)
@@ -1895,7 +1896,14 @@ catch(MinioException e)
     Console.WriteLine("Error occurred: " + e);
 }
 ```
-
+**Remark:** 
+Note that the default [Progress<T> class](https://learn.microsoft.com/en-us/dotnet/api/System.Progress-1) post progress
+updates to the SynchronizationContext when the instance was constructed
+([source](https://learn.microsoft.com/en-us/dotnet/api/system.progress-1#remarks)). This means that progress updates are
+sent asynchronous. If you do want to receive the events synchronous, then use the `Minio.Helper.SyncProgress<T>` instead,
+but make sure you understand the implications. Progress events are sent synchronous, so they may be invoked on an
+arbitrary thread (mostly a problem for UI applications) and performing long-running and/or blocking operations will
+degrade upload performance.
 
 <a name="statObject"></a>
 ### StatObjectAsync(StatObjectArgs args)

Minio.Examples/Program.cs

@@ -24,6 +24,7 @@
 using Minio.DataModel.Notification;
 using Minio.DataModel.ObjectLock;
 using Minio.Examples.Cases;
+using Minio.Helper;
 
 namespace Minio.Examples;
 
@@ -110,7 +111,7 @@ public static async Task Main()
         var destBucketName = GetRandomName();
         var destObjectName = GetRandomName();
         var lockBucketName = GetRandomName();
-        var progress = new Progress<ProgressReport>(progressReport =>
+        var progress = new SyncProgress<ProgressReport>(progressReport =>
         {
             Console.WriteLine(
                 $"Percentage: {progressReport.Percentage}% TotalBytesTransferred: {progressReport.TotalBytesTransferred} bytes");

Minio.Functional.Tests/FunctionalTest.cs

@@ -3495,7 +3495,7 @@ internal static async Task PutObject_Test9(IMinioClient minio)
         const string contentType = "application/octet-stream";
         var percentage = 0;
         var totalBytesTransferred = 0L;
-        var progress = new Progress<ProgressReport>(progressReport =>
+        var progress = new SyncProgress<ProgressReport>(progressReport =>
         {
             percentage = progressReport.Percentage;
             totalBytesTransferred = progressReport.TotalBytesTransferred;
@@ -3552,7 +3552,7 @@ internal static async Task PutObject_Test10(IMinioClient minio)
         var contentType = "binary/octet-stream";
         var percentage = 0;
         var totalBytesTransferred = 0L;
-        var progress = new Progress<ProgressReport>(progressReport =>
+        var progress = new SyncProgress<ProgressReport>(progressReport =>
         {
             percentage = progressReport.Percentage;
             totalBytesTransferred = progressReport.TotalBytesTransferred;

Minio/Helper/SyncProgress.cs

@@ -0,0 +1,29 @@
+namespace Minio.Helper;
+
+/// <summary>
+///     SyncProgress is a thread-free alternative to <see cref="System.Progress&lt;T&gt;" />
+///     and should be used if progress needs be determined in real-time.
+/// </summary>
+/// <typeparam name="T"></typeparam>
+/// <remarks>
+///     The upload process uses asynchronous tasks to perform the upload,
+///     so these events may be invoked on an arbitrary thread. Use the
+///     regular <see cref="System.Progress&lt;T&gt;" /> if you need progress
+///     to be reported on a fixed thread or provide your own thread
+///     synchronization. Doing synchronous calls to other threads from
+///     within this handler will degrade your upload performance.
+/// </remarks>
+public class SyncProgress<T> : IProgress<T>
+{
+    private readonly Action<T> handler;
+
+    public SyncProgress(Action<T> handler)
+    {
+        this.handler = handler;
+    }
+
+    public void Report(T value)
+    {
+        handler(value);
+    }
+}