Wednesday, December 9, 2009

Boo web console

Here's another embeddable web console: a Boo interpreter. You enter some code, hit the Execute button and it compiles and runs the code. You get access to all of the assemblies in your app.

I use this to run short ad-hoc "queries" against a running web app, like:

  • Is this thing in the cache?
    print (context.Cache["pepe"] == null)
  • Do I have all httpmodules correctly registered?
    import System.Web
    for s in context.ApplicationInstance.Container.ResolveAll(typeof(IHttpModule)):
      print s
  • Checking performance counters:
    import System.Diagnostics
    pc = PerformanceCounterCategory("ASP.NET")
    for counter in pc.GetCounters():
      print counter.CounterName, counter.NextValue()
  • Or even running some NHibernate query (although I'd prefer using the NHibernate web console):
    import NHibernate 
    sf = context.ApplicationInstance.Container.Resolve(typeof(ISessionFactory)) 
    using s = sf.OpenSession(): 
      users = s.CreateQuery("from User order by newid()").SetMaxResults(5).List()
      for u in users: 
        print u.Id 

Why Boo? Because it's pretty much the perfect .net scripting language to embed: small (this console with boo merged in is about 1.9MB), type inference, duck typing, low-ceremony syntax.


  • Put BooWebConsole.dll in your app's bin directory
  • Add it to your web.config's <httpHandlers> section:
    <add verb="*" path="boo/*" validate="false" type="BooWebConsole.ControllerFactory, BooWebConsole"/>
  • Visit /boo/index.ashx


  • Unlike booish, this console is stateless. Each http request creates a new interpreter, it doesn't remember anything you executed in previous requests.
  • Since the code is compiled and run within the main AppDomain, this will leak memory. Not a big deal in a dev environment though. But putting this in a production site is pretty much suicidal.
  • In case it isn't obvious: this is not meant to replace proper testing.

Code is here.

UPDATE: it's now also available on NuGet

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