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Alternatives to Reflector that I tried: ILSpy (from SharpDevelop), DotPeek (from JetBrains) and JustDecompile (from Telerik) – none of them cut it

Posted by jpluimers on 2012/07/24

A long time ago, I wrote about the Reflector debacle and the URLs how it used to update. Since then Reflector came out. No newer free versions will be released, and RedGate randomized parts of the URLs to make it harder to upgrade if you do not have version around (if you really want you can go around that too).

So I’ve been using some alternatives for a while: ILSpy by SharpDevelop (open source), dotPeek by JetBrains and JustDecompile by Telerik (both closed source).

There are more (monoflector, Kaliro App Explorer, Dotnet IL Editor, Dis#, StackOverflow threads and various sites describing more) but I discuss the ones I used.


Installation means unzipping the download and running the EXE in it. Plain simple.

After starting ILSpy, you see that the GUI mimics Reflector. That raises expectations. Not sure if that is good (:

F3 works similar to Reflector, but you cannot search for System.String (bad), you have to search for “String” or “string” which results in “System.String” to be the topmost entry. Good: as now pressing Down and Enter will get you to System.String.

Disassembly is like Reflector, however, it collapses all code regions, and there seems no way to unfold those in one go. Not good.

You cannot click on built in types like int and string to navigate to their framework counterparts like you can in Reflector. Not good.

Searching and clikcing is fast. No time lag.

The “Analyze” feature is like the “Find References” feature in Reflector. It is fast too. Good.


Installation means unzipping the download and running the EXE in it. Plain simple.

dotPeek is a lot slower than Reflector was.

Sorting assemblies by versions is strange: first you get, then 1.x.y.z, then 10.x.y.z, then 11.x.y.z, then 2.x.y.z. Apparantly nobody of the dotPeek team ever sorts by version.

The easiest way to load the .NET 4.0 framework from the GAC, is sort by version, search for System.* and select everything that has version Not good.

F3 doesn’t work as a search for symbol shortcut (like it did in Reflector) but maps to Ctrl-F (find in current source code). To find symbols you need Ctrl-T, which takes forever to load a symbol list. Not good.

You cannot click on built in types like int and string to navigate to their framework counterparts like you can in Reflector. Not good.


The installer tries to get you hooked to the non-free JustCode and JustTrace. I hate it when installers do that.

The GUI of the installer has the checkboxes scattered over the dialog, and has so little contrast in colors, that you need to look twice to see what is enabled and what not. Their install builders clearly need to use their install GUI more often.

You also need to provide all sorts of info in order to sign up for an account (firstname, lastname, company, email and country? luckily the IANA example domains and work fine for that). Too bad that Example didn’t work as country. The auto-completion made “El Salvador” out of it. Fine. Now Telerik has a new client Example Exampl working at Example with email living in El Salvador. Good luch with that.

The installer then downloads a zillion megabytes (hey, what about providing an offline installer!) and takes minutes to install and display marketing material (which I couldn’t see because I switched away doing some useful work; at least this installer allows switching away from it, unlike many obnoxious installers that think they are the most important asset on your screen).

You can start it my pressing your Windows key, then typing JustDecompile (No spaces needed. Good!).

One good GUI aspect is that it allows you to load the .NET 4.0, 3.5, 2.0 or Silverlight framework assemblies each as a set.

The list for the 4.0 framework is way bigger than Reflector used to load, which is good as it always took me forever to get manually open those from the GAC in Reflector.

Searching for classes is a nightmare, as you can only type the classname, not the namespace. So searching for System.String (which works dandy in Reflector) results in “no results were found”. You have to search for “String”, then select from a huge list. Also, pressing Down then Enter doesn’t select the topmost entry in the searched list like Reflector did. Both points not good.

The GUI is slow. If you click on anything, it lags before displaying new information. Reflector is snappy. JusDecompile is not. It also doesn’t show a wait cursor when it lags, so you risk clicking on multiple things before realising that it was working in the background.

Decompiling works  nice: syntax highlighted source code where you can click on any references and it will follow (with a lag) the reference.
Decompile only supports the Visual Basic, C# (default), and IL languages.

Like Reflector, you can click on built in types like int and string to navigate to their framework counterparts. Good.

“Finding usages” is similar to “Finding References” in Reflector. But it is slower, and doesn’t show the progress of the search which means you don’t know how long the search will take. It also doesn’t remember the search history that Reflector does.

You cannot dock the “Find Usages” or “Search” windows, which means they will partially obstruct the decompiled code view (unless you put those windows on a secondary monitors or make the main window smaller).


More than a year after Redgate announced that Reflector would become commercial, the alternatives are, well basically not real alternatives.

I was hoping to use Reflector only when I’m lazy, and fall back on stuff that has settled in my premotor cortex.

That is not the case.

Reflector 6 (of which the majority basically is the work of one man: Lutz Roeder) still is far ahead of any similar things.


10 Responses to “Alternatives to Reflector that I tried: ILSpy (from SharpDevelop), DotPeek (from JetBrains) and JustDecompile (from Telerik) – none of them cut it”

  1. Vladi said


    Thanks for the review and unbiased review. You’ve caught real JustDecompile issues and we’ll work on improving them.

    A bit more details:

    – the installer experience – I’ll forward all your comments to the teams involved as this is important to know. As a workaround you can always use our two offline installer versions: MSI and ZIP installers which you can find on the “Thank You” page after downloading the Web installer, and here (only the MSI):

    – searching for classes (namespaces) – it’s already on our ToDo list and we’ll work on this with higher priority.

    – slowness of GUI – this is not expected behavior. Can you please share what your PC hardware spec is and whether you run JustDecompile together with Reflexil?

    – slowness of “Find Usages” – the answers to the questions from above for the GUI slowness will help us here as well

    – progress bar and search history for “Find Usages” – actually “Find Usages” has progress spinning wheel while it searches (in the bottom left corner) and remembers the search results in the current session. We don’t remember the search history between sessions. We’ll consider the idea but if you’d like to raise the priority of this task you can always help us by suggesting it as feature request in our UserVoice website:

    – docking “Find Usages” and “Search” windows – it is on our radar and we’ll work on it. Again you can raise its priority by suggesting it on the UserVoice website.

    Also if you come upon any other issues or have more feedback, you are more than welcome to share them in our forum as well:

    The Telerik team

    • jpluimers said

      I did most of the testing at the end of march with the versions of tools available then. I think it was on my main dev machine in a VMware VM with W7 x64 dual CPU 1.6 Ghz and 2 Gb of RAM and SSD disk.

      Right now I’m in 3 crunch mode projects for the next 4-5 weeks. Ping me back then, I’ll retest with the current versions.

      Then my ESXi5 development box should be ready as well (2.5 Ghz Xeon CPUs with VMs having 4 Gb of RAM, and a RAID SATA array backing store) which makes it easier to switch development environments.

      I’m not so much a forum guy, as they are a bit cumbersome to keep track of (especially with the amount of development products I am using). I wish forums could integrate into something like StackExchange more easily as that is pretty OK to keep track of (currently that only works when you get through the Area51 process). Wishes for the future (:

  2. Dude, I think you completely missed it with dotPeek :). When it comes to navigation it kills everything else. You get the entire Navigation features that ReSharper offers you in dotPeek. Use the same shortcuts. Try Alt+[. Try F12 to go to definition, try Ctrl+T, Shift+Ctrl+T, Alt+\. You’re missing it all.

    • jpluimers said

      Thanks mate (: Will try that. A bit more compatibility with existing Reflector stuff would be welcome though. Not all usability aspects of Reflector are bad. And if you guys start working on performance, that would be awesome, as that is currently my biggest issue with dotPeek (;

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