Create System.Windows.Media.Color in IronPython

Question

Im using IronPython and i try to instantiate a color from script and return it. I got this method and send in this string as an argument

@"
from System.Windows.Media import Color
c = Color()
c.A = 100
c.B = 200
c.R = 100
c.G = 150
c
");

_python = Python.CreateEngine();

public dynamic ExectureStatements(string expression)
{
    ScriptScope scope = _python.CreateScope();
    ScriptSource source = _python.CreateScriptSourceFromString(expression);
    return source.Execute(scope);
}

When I run this code I get

$exception {System.InvalidOperationException: Sequence contains no matching element at System.Linq.Enumerable.First[TSource](IEnumerable`1 source, Func`2 predicate).. etc.

I can not figure out how to get this to work, so please help me.

Answer 1

I won't know for sure until I see either more of your source or the full stack, but I would guess you're missing having the python engine include a reference to the necessary WPF assemblies (PresentationCore for System.Windows.Media.Color AFAICT).

Depending on whether you care about the C# caller needing a reference to the same library, you can change how it gets a reference to it, but just adding PresentationCore lets me reference the necessary assembly (without strings :) and then add it to the IronPython runtime.

The below code runs fine and prints out #646496C8

using System;
using IronPython.Hosting;
using Microsoft.Scripting.Hosting;

class Program
{
    private static ScriptEngine _python;
    private static readonly string _script = @"
from System.Windows.Media import Color
c = Color()
c.A = 100
c.B = 200
c.R = 100
c.G = 150
c
";


    public static dynamic ExectureStatements(string expression)
    {
        var neededAssembly = typeof(System.Windows.Media.Color).Assembly;
        _python.Runtime.LoadAssembly(neededAssembly);
        ScriptScope scope = _python.CreateScope();
        ScriptSource source = _python.CreateScriptSourceFromString(expression);
        return source.Execute(scope);
    }

    static void Main(string[] args)
    {
        _python = Python.CreateEngine();
        var output = ExectureStatements(_script);
        Console.WriteLine(output);
    }
}