Grasshopper + rhino plugin + Sql-listener -> what's the correct C# design pattern?

Hi all,

We're writing a rhino-plugin to open/run/close a .ghx files in an open instance of rhino/grasshopper. I would like the plugin to get notified if a new item is added in the queue (a mssql database running on the same local machine).

I came up with a solution but i'm looking for a better code pattern since this one has the Rhino+Grasshopper UI locked in the RhinoMainWindow thread. (since rhino is not threadsafe)

Current Solution:

The RhinoPlugin main thread waits for an 'EventWaitHandle' from a seperate thread that gets notified through an SqlDependency. If it receives the event it opens the .ghx file and performs some actions. After it's done it just starts a new SqlDependency. The beauty is that since Rhino is single-threaded you don't run into problems since you just wait. So you can simply stear the rhino/gh instances to do whatever you like.

The downside is the UI is completely locked during the waiting.

Alternative ideas:

- use a windows.forms.timer (single threaded) to poll the database with a normal query every 500ms. This probably won't lock the UI but can be 500ms slower plus the extra query-overload.

- ?

I'm looking forward to any ideas/suggestions/experiences. All thoughts are appreciated!

cheers,

Elco

Replies to This Discussion

Permalink Reply by Elco on June 27, 2013 at 3:26am

@David,

Hi David, do you have any suggestions to this topic?

thx,

Elco & Jan

Delft

Permalink Reply by David Rutten on June 27, 2013 at 7:07am

Once you get the event, why not invoke a method on the Rhino main UI thread which starts your Rh+GH logic?

David Rutten

david@mcneel.com

Tirol, Austria

Permalink Reply by Elco on July 1, 2013 at 2:40pm

Hi David,

Yes i tried that, but i think i invoked on the wrong part or something since GH threw me a very undefined error that it couldn't open a file. I guess it had to do with threading.

Is this the correct way to invoke a method on rhino's main thread?

if(RhinoApp.MainApplicationWindow.InvokeRequired)
{
RhinoApp.MainApplicationWindow.Invoke(MyDelegateMethod);
}

thx,

Elco

Permalink Reply by Elco on July 3, 2013 at 5:48am

Hi David,

The above worked out. I just had to make sure all grasshopper related instances were inside the scope and thread of MyDelegateMethods.

thanks for your hint.

have a nice day,

Elco

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