access host class from IronPython script (lightswitch)

Question

I'm new at this, so I hope the question is well formed enough for someone to understand what i'm asking, if not I'm happy to add more detail. I am trying to reference a variable defined on the server side of a lightswitch application from a python script. The following post explains how to access a host class from a python script.

Access host class from IronPython script

The code on my server side is

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.LightSwitch;
using Microsoft.LightSwitch.Security.Server;
using System.IO.Ports;
using System.Threading;
using IronPython.Hosting;

namespace LightSwitchApplication
{
 public partial class ApplicationDataService     
{
    partial void ServerCommands_Inserting(ServerCommand entity)
    { 
        switch (entity.ClientCommand)
        {
            case "RunPythonScript":


             var engine = Python.CreateEngine();
             var searchPaths = engine.GetSearchPaths();
             searchPaths.Add(@"C:\Temp");
             engine.SetSearchPaths(searchPaths);

             var mainfile = @"C:\Temp\script.py";
             var scope = engine.CreateScope();
             engine.CreateScriptSourceFromFile(mainfile).Execute(scope);
             var param1 = entity.Param1;                       
             engine.Execute(scope);

How do i reference the server side variable below from the Python script?

entity.Param1

In the python script I've attempted to import a server side class that would allow me access to the variable

import clr
clr.AddReference("Microsoft.Lightswitch.Application")

but the .Server reference is not available...only the .Base is available.

from Microsoft.Lightswitch.Framework.Base import

I have no idea if the Framework.Server class is even the right one, just guessing at this point. Thanks!

Answer 1

You could simply set entity as a variable of your scope. You also could pass it to a function in script.py. For example:

Your python script:

class SomeClass:
    def do(self, entity):
        print entity.Param1

Your c# code will look like this:

var engine = Python.CreateEngine();
var searchPaths = engine.GetSearchPaths();
searchPaths.Add(@"C:\Temp");
engine.SetSearchPaths(searchPaths);

var mainfile = @"C:\Temp\script.py";
var scope = engine.CreateScope();

// Execute your code
engine.CreateScriptSourceFromFile(mainfile).Execute(scope);
// Create a class instance
var type = scope.GetVariable("SomeClass");
var instance = engine.Operations.CreateInstance(type);
// Call `do` method
engine.Operations.InvokeMember(instance, "do", entity); // PASS YOUR ENTITY HERE

After this, you can access your complete entity in the IronPython script. You don't need clr.AddReference("Microsoft.Lightswitch.Application").

Also, the second execute (engine.Execute(scope);) seems to be not neccessary. Maybe this helps you.