CacheItemPolicy with HostFileChangeMonitor takes time to clean the cache

[Chizkiyahu]

When I use CacheItemPolicy with HostFileChangeMonitor and the file changed is taking 5-7 ms for cache to remove the item

[TestMethod]
public void TestHostFileChangeMonitor()
{
    var cachedFilePath = @"c:\temp\123.txt";
    File.WriteAllText(cachedFilePath, "1111");
    System.Runtime.Caching.ObjectCache cache = MemoryCache.Default;
    string fileContents = cache["filecontents"] as string;
    if (fileContents == null)
    {
        CacheItemPolicy policy = new CacheItemPolicy();
        List<string> filePaths = new List<string>();
        filePaths.Add(cachedFilePath);

        policy.ChangeMonitors.Add(new
            HostFileChangeMonitor(filePaths));

        // Fetch the file contents.  
        fileContents = File.ReadAllText(cachedFilePath);
        cache.Set("filecontents", fileContents, policy);
    }
    File.WriteAllText(cachedFilePath, "2222");
    int sleepTime = 5;
    Thread.Sleep(sleepTime);
    string fileContents2 = cache["filecontents"] as string;
    Assert.AreEqual("2222", File.ReadAllText(cachedFilePath));
    // the test past only if  sleepTime > 5 
    Assert.IsNull(fileContents2);
}

Pay attention without sleep the test fail with 5-7 ms sleep is past

Configuration

windows 10
visual studio professional
net framework 4.6.1

Analysis

My solution

[Dotnet-GitSync-Bot]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[Chizkiyahu]

area-System.Runtime.Caching

[HongGit]

@Chizkiyahu what exactly is the issue? Is this blocking your scenario? If so, could you please elaborate more? Have you done any comparison with .NET framework? Is this a regression from .NET Framework?

[Chizkiyahu]

@HongGit I use the CacheItemPolicy for cache for xml files and after the state change and the file changed i expecting from HostFileChangeMonitor to remove from the cache but the bug is the cache return the file and is the old state

I fix that bug in my code by check the last time the file change is bigger than is enterd to the cache