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The Black Box of .NET

Tuesday, May 14, 2019

Unifying .NET

One framework to rule them all?

.NET 5 is on the way and scheduled to be delivered in November 2020. It is meant to unify .NET Framework, .NET Core, Mono (and possibly .NET Standard) - i.e. the entire .NET Platform.

After 17 years of working in .NET (since it was first released in 2002), I'm excited to see a unified solution to the splintered framework that .NET has become as of late.  IMO, .NET Framework, .NET Core, .NET Standard, and Mono have grown into a big bad monster that is growing faster than its parts can manage. While we know (and expect) technology to evolve and grow over time, we hope that it doesn't fragment and splinter so much that its parts become dissimilar.  I've seen it grow from a set of APIs that were questionable to something that is almost overwhelming - and certainly difficult to keep up with.  I'm pleased to see that Microsoft has acknowledged the splintering and has been working on a solution since at least December 2018.  I'm looking forward to seeing how much simpler things will become.

Now if they could just FINALLY fix "Edit and Continue"...........

(image is copyright of Microsoft)


Friday, April 19, 2019

Missing Start Page from Visual Studio 2019

Oh Microsoft, why hast thou forsaken the beloved 'Start Page' and replaced it with a modal window?

The new 'Start Window' which replaces the 'Start Page'

You can see the design reasoning behind the new VS 2019 Start Window as posted at 'Get to code: How we designed the new Visual Studio start window' and 'New Start Window and New Project Dialog Experience in Visual Studio 2019'.

I sincerely appreciate any amount of thought, consideration, or testing that a company decides to invest in their products - especially a flagship produce like Visual Studio.  Based on the design reasoning Microsoft certainly had good intentions and did put a good amount of thought and testing into the effort.  However, I think they missed the mark.  Perform any Google search on "missing start page visual studio 2019" or look on the Developer Community Feedback Site and you'll see devs crying out for the beloved Start Page.

Some things are better left untouched and left alone and the Start Page is one of them. Some might argue the new 'Start Window' is a better experience but why make it a modal window?  Really?  In Visual Studio 2019 Preview 1, at least the option to restore the 'Start Page' was available as an option in the Startup settings:

However, somewhere along the way the 'Start Page' item has disappeared from the drop-down...headsmack!  Here's what the options are in version 16.0.2:

Ok, now I'm getting frustrated.  I get it. You're trying to funnel me into this new window that you think is better.  Well, my response is

Fortunately, Microsoft hasn't completely done away with the 'Start Page'...yet.  You can still add it by customizing the toolbar to add the Start Page button:

1. Right-click the toolbar and select 'Customize':

2. Select the 'Commands' tab:

3. Select 'Toolbar' and change the dropdown to whatever menu you'd like, then click the 'Add Command' button:
4. Choose 'File' from the Categories list box, then select 'Start Page' from the Commands list box:

So, there you go!  At least it's still there for now.  I'd bet any amount of money that they change the experience back so that either the 'Start Page' option is available from the Environment/Startup setting. To be fair, Microsoft has improved significantly at listening to community feedback.

Thursday, March 5, 2015

Angular2 and TypeScript

This is awesome for the Client side scripting world! I LOVE both of the languages and the features and safety of each.  Great collaboration!


Wednesday, February 18, 2015

HTTP 2 is finally done

Finally the specs for HTTP 2 were finalized yesterday and will be integrated into Chrome 40 and a new FireFox coming over the next 10-12 weeks.  Here are some of the things to expect.

Wednesday, September 10, 2014

How not to do Dependency Injection

Dependency Injection (DI) is not a new concept and has been discussed, blogged, and published many times.  There are a huge number of books out there on the subject.  I've seen many usages and implementations of it used by various clients I've consulted for. 

Like the author of the blog post I refer to below, one of the most common and mis-used, abuses of, and antipatterns I've seen is the wrapping of the DI model in a static container.

I recently found an excellent article that explains in great detail why this is a bad idea and a big anti-pattern -

Hopefully, this will help improve your understanding of what DI is and how it should not be used.

Thursday, May 24, 2012

References to missing Types or Methods in referenced DLL

Ever wonder what happens if you have a binary reference to an external .dll and decide not to recompile the application or library that references/depends on it? You can get some strange errors depending on the changes that have been made. Ever experienced a BadImageFormatException, ExecutionEngineException, TypeLoadException, or MissingMethodException?

Firstly, the manifest file for the dependent app/library is not updated pointing to the new version. This can cause mismatched assembly version errors (BadImageFormatException).

Here are the results from some tests with the removal of types and/or methods on a referenced assembly (hereinafter referred to as ‘Bad Assembly’). All tests were done with x86 Console App/Library in separate solutions with a “static hardcoded” path reference to Bad Assembly (x64 shouldn’t matter):
  1. Results were always the same for Release/Debug builds.
  2. The bad assembly was always successfully loaded. ‘fuslogvw’ (.NET Assembly Load Viewer) confirmed this.
  3. Setting the reference to Bad Assembly as “Specific Version” (using v1.0.0.0) and changing the version on Bad Assembly to v1.1.0.0 had no effect. However, I didn’t try defining Bad Assembly in the “assemblies” section of the app.config. It is possible that would have given a different result.
  4. References to a missing Type OR calls to a missing Method from Bad Assembly in "static void Main()" resulted in a "System.ExecutionEngineException" (fatal error as shown below). This exception cannot be caught by any means: Assembly events, AppDomain events, try/catch block in "static void Main()". I confirmed this thru WinDbg. This is because it is the first method that the EE (CLR Execution Engine) tells the JIT to compile. Since JIT happens on a method-by-method basis and "static void Main()" is the entry point for the app, there is no place “upstream” where an exception can be caught. The error in the Event Viewer is completely cryptic and provides no indication what went wrong.
  5. If the reference to a missing Type OR calls to a missing Method from Bad Assembly occurred “downstream” of "static void Main()" AND there WAS NOT exception handling upstream, OR there WAS exception handling upstream but the exception was rethrown so that is was never caught again, then results were same as #4.  (i.e. unhandled exception)
  6. If the reference to a missing Type OR calls to a missing Method from Bad Assembly occurred “downstream” of "static void Main()" AND there WAS exception handling upstream, then the exception was caught as either a "System.TypeLoadException" or "System.MissingMethodException" respectively.  The exceptions were thrown from the JIT as the Type or Method was accessed.



Friday, May 18, 2012

Why you should use ReadOnlyCollection<T>

Many people believe that you should be using List<T> to return collections from a public API.  However, there are several reasons not to do so; instead return a ReadOnlyCollection<T>. The are several benefits of using a ReadOnlyCollection<T>:
  1. The *collection itself* cannot be modified – not the items within it. i.e. you cannot add, remove, or replace any item in the collection. So, it keeps the collection itself intact – not the values of the items within it. To protect the items in it, you’d probably have to have private “setters” on any properties for the reference object in the collection – which is generally recommended. However, items that are declared as [DataMember] must have both public getters and setters. So if you are in that case, you can’t do the private setter, but you can still use the ReadOnlyCollection<T>. Using this as a Design paradigm can prevent subtle bugs from popping up.
  2. Performance: The List<T> class is essentially a wrapper around a strongly-typed array. Since arrays are immutable (cannot be re-sized), any modifications made to a List<T> must create a complete copy of List<T> and add the new item. The initial capacity for a List<T> is ‘4’ unless specified thru the overloaded constructor. Obviously this can be very bad for memory and performance. Don’t forget that not only the items directly within the List<T> are copied – but every value and object with the entire object graph for that reference type – this could easily contain other references type, other collections, etc. This is why it is best practice to create/initialize a List<T> instance with the overloaded constructor which takes an ‘int’ denoting the size of the List to be created. This can almost always be done since you are usually iterating on a “known” size value at runtime. For example, creating a List<T> of objects from a "Repository or DataService" method usually iterates/reads from a IDataReader object which has a property of ‘RecordsAffected’. If you are going to be putting an item in the List<T> based on the number of times the IDataReader is Read – while(reader.Read()) you can easily create the list like so (and it is preferable to do it like this):
    if (reader != null && reader.RecordsAffected > 0)
        List<Foo> someList = new List<Foo>(reader.RecordsAffected);
        while (reader.Read())

Just as a side note…every time that a List<T> needs to grow in size, the size is *doubled*. So, if you happen to add just one more item to a List<T> that wasn’t constructed with a pre-determined size, and the List<T> expands to accommodate the new item, there will be a whole lot of unused space at the end of the List<T> even though there aren’t any items in it – bad for memory and performance.

Thursday, May 17, 2012

Don't implement GetHashCode() on mutable fields/properties

CodeProject You shouldn't ever implement GetHashCode on mutable properties (properties that could be changed by someone) - i.e. non-private setters.   I've seen this done in several places and it results in very difficult to find bugs.

Here's why - imagine this scenario:
  1. You put an instance of your object in a collection which uses GetHashCode() "under the covers" or directly (Hashtable).
  2. Then someone changes the value of the field/property that you've used in your GetHashCode() implementation.
Guess what...your object is permanently lost in the collection since the collection uses GetHashCode() to find it! You've effectively changed the hashcode value from what was originally placed in the collection. Probably not what you wanted.

Tuesday, April 17, 2012

How to determine which garbage collector is running

CodeProjectYou can determine which version of GC you're running via 2 methods:
  1. calling the System.Runtime.GCSettings.IsServerGC property
  2. attaching to the process using WinDbg and checking how many GC threads you have using the command "!sos.threads" without the quotes and (according to the below criteria)...
If you are running a Console app, WinForm app or a Windows Service, you will get the Workstation GC. Just because you are running on a Server OS doesn't mean that you will get the Server version of GC.
  • If your app is non-hosted on a multi-proc machine, you will get the Workstation GC - Concurrent by default.
  • If your app is hosted on a multi-proc machine, you will get the ServerGC by default.
The following apply to any given .NET Managed Process:

Workstation GC

  • Uni-processor machine
  • Always suspends threads
  • 1 Ephemeral GC Heap (SOH), 1 LOH GC Heap
  • Runs on thread that triggered GC
  • Thread priority is the same as the thread that triggered GC

Workstation GC - Concurrent

  • Only runs concurrent in Gen2/LOH (full collection)
  • Mutually exclusive with Server Mode
  • Slightly larger working set
  • GC Thread expires if not in use after a while
  • 1 Ephemeral GC Heap (SOH), 1 LOH GC Heap
  • Has a dedicated GC Thread
  • Thread priority is Normal

Server GC

  • Larger segment sizes
  • Faster than Workstation GC
  • Always suspends threads
  • 1 Ephemeral GC Heap (SOH) for each logical processor (this includes hyperthreaded), 1 LOH GC Heap for each logical processor (this includes hyperthreaded)
  • Has dedicated GC Threads
  • Thread priority is THREAD_PRIORITY_HIGHEST
There is only 1 Finalizer thread per managed process regardless of GC Mode. Even during a concurrent GC, managed threads are suspended (blocked) twice to do some phases of the GC.

A seldom known fact is that even if you try to set the Server mode of GC, you might not be running in Server GC; the GC ultimately determines which mode will be optimal for your app and WILL override your settings if it determines your ServerGC setting will negatively impact your application. Also, any hosted CLR app will have any manual GC settings overridden.

In CLR 4.0, things change just a little bit

  • Concurrent GC is now Background GC
  • Background GC only applies to Workstation GC
  • Old (Concurrent GC):
    • During a Full GC Allowed allocations up to end of ephemeral segment size
    • Otherwise, suspends all other threads
  • New (Background GC):
    • Allows for ephemeral GC’s simultaneously with Background GC if necessary
    • Performance is much faster
  • Server GC always blocks threads for collection of any generation

In CLR 4.5, things change just a little bit...again

  • Background Server GC
    • Server GC no longer blocks. Instead, it uses dedicated background GC threads that can run concurrently with user code - see MSDN: Background Server GC
Thus, in .NET 4.5+, all applications now have background GC available to them, regardless of which GC they use.

.NET 4.7.1 GC Improvements

.NET Framework 4.7.1 brings in changes in Garbage Collection (GC) to improve the allocation performance, especially for Large Object Heap (LOH) allocations. This is due to an architectural change to split the heap’s allocation lock into 2, for Small Object Heap (SOH) and LOH. Applications that make a lot of LOH allocations, should see a reduction in allocation lock contention, and see better performance. These improvements allow LOH allocations while Background GC (BGC) is sweeping SOH. Usually the LOH allocator waits for the whole duration of the BGC sweep process before it can satisfy requests to allocate memory. This can hinder performance. You can observe this problem in PerfView’s GCStats where there is an ‘LOH allocation pause (due to background GC) > 200 msec Events’ table. The pause reason is ‘Waiting for BGC to thread free lists’. This feature should help mitigate this problem.

Tuesday, March 13, 2012

Don't use 'using()' with a WCF proxy

If you're trying to be a conscientious developer and making sure that you cleanup your resources - great! You are writing 'using()' blocks around all of your disposable items - great...except when the disposable item is a WCF Client/Proxy! The using() statement and the try/finally effectively have the same IL:

    // The IL for this block is effectively the same as
    // the IL for the second block below
    using (var win = new Form())

    // This is the second block
    Form f = null;
        f = new Form();
        if (f != null)

Here's the IL for the 'using()' block above compiled in Release mode:

     IL_0000:  newobj     instance void [System.Windows.Forms]System.Windows.Forms.Form::.ctor()
     IL_0005:  stloc.0
         IL_0006:  leave.s    IL_0012
     }  // end .try
         IL_0008:  ldloc.0
         IL_0009:  brfalse.s  IL_0011
         IL_000b:  ldloc.0
         IL_000c:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
         IL_0011:  endfinally
     }  // end handler

Here's the IL for the second block (try/finally) compiled in Release mode:

     IL_0012:  ldnull
     IL_0013:  stloc.1
         IL_0014:  newobj     instance void [System.Windows.Forms]System.Windows.Forms.Form::.ctor()
         IL_0019:  stloc.1
         IL_001a:  leave.s    IL_0026
     }  // end .try
         IL_001c:  ldloc.1
         IL_001d:  brfalse.s  IL_0025
         IL_001f:  ldloc.1
         IL_0020:  callvirt   instance void [System]System.ComponentModel.Component::Dispose()
         IL_0025:  endfinally
     }  // end handler

As you can see, the IL is nearly identical.

Well this is all fine and good but let's get back to the issue with WCF.  The problem is that if an exception is thrown during disposal of the WCF client/proxy, the channel is never closed.  Now, in general, any exception that occurs during disposal of an object is indeed undesirable.  But, in the case of WCF, multiple channels remaining open could easily cause your entire service to fall on its face - not to mention what might eventually happen to your web server.

Here is an alternative solution that can be used:

    WCFProxy variableName = null;
        variableName = new WCFProxy();

        // TODO code here

// if you need to catch other exceptions, do so here...
    catch (Exception)
        if (variableName != null)

MSDN does have a brief on this issue which you can read here -