What is the best scripting language to embed in a C# desktop application? [closed]

Personally, I'd use C# as the scripting language. The .NET framework (and Mono, thanks Matthew Scharley) actually includes the compilers for each of the .NET languages in the framework itself.

Basically, there's 2 parts to the implementation of this system.

  1. Allow the user to compile the code This is relatively easy, and can be done in only a few lines of code (though you might want to add an error dialog, which would probably be a couple dozen more lines of code, depending on how usable you want it to be).

  2. Create and use classes contained within the compiled assembly This is a little more difficult than the previous step (requires a tiny bit of reflection). Basically, you should just treat the compiled assembly as a "plug-in" for the program. There are quite a few tutorials on various ways you can create a plug-in system in C# (Google is your friend).

I've implemented a "quick" application to demonstrate how you can implement this system (includes 2 working scripts!). This is the complete code for the application, just create a new one and paste the code in the "program.cs" file. At this point I must apologize for the large chunk of code I'm about to paste (I didn't intend for it to be so large, but got a little carried away with my commenting)


using System;
using System.Windows.Forms;
using System.Reflection;
using System.CodeDom.Compiler;

namespace ScriptingInterface
{
    public interface IScriptType1
    {
        string RunScript(int value);
    }
}

namespace ScriptingExample
{
    static class Program
    {
        /// 
        /// The main entry point for the application.
        /// 
        [STAThread]
        static void Main()
        {

            // Lets compile some code (I'm lazy, so I'll just hardcode it all, i'm sure you can work out how to read from a file/text box instead
            Assembly compiledScript = CompileCode(
                "namespace SimpleScripts" +
                "{" +
                "    public class MyScriptMul5 : ScriptingInterface.IScriptType1" +
                "    {" +
                "        public string RunScript(int value)" +
                "        {" +
                "            return this.ToString() + \" just ran! Result: \" + (value*5).ToString();" +
                "        }" +
                "    }" +
                "    public class MyScriptNegate : ScriptingInterface.IScriptType1" +
                "    {" +
                "        public string RunScript(int value)" +
                "        {" +
                "            return this.ToString() + \" just ran! Result: \" + (-value).ToString();" +
                "        }" +
                "    }" +
                "}");

            if (compiledScript != null)
            {
                RunScript(compiledScript);
            }
        }

        static Assembly CompileCode(string code)
        {
            // Create a code provider
            // This class implements the 'CodeDomProvider' class as its base. All of the current .Net languages (at least Microsoft ones)
            // come with thier own implemtation, thus you can allow the user to use the language of thier choice (though i recommend that
            // you don't allow the use of c++, which is too volatile for scripting use - memory leaks anyone?)
            Microsoft.CSharp.CSharpCodeProvider csProvider = new Microsoft.CSharp.CSharpCodeProvider();

            // Setup our options
            CompilerParameters options = new CompilerParameters();
            options.GenerateExecutable = false; // we want a Dll (or "Class Library" as its called in .Net)
            options.GenerateInMemory = true; // Saves us from deleting the Dll when we are done with it, though you could set this to false and save start-up time by next time by not having to re-compile
            // And set any others you want, there a quite a few, take some time to look through them all and decide which fit your application best!

            // Add any references you want the users to be able to access, be warned that giving them access to some classes can allow
            // harmful code to be written and executed. I recommend that you write your own Class library that is the only reference it allows
            // thus they can only do the things you want them to.
            // (though things like "System.Xml.dll" can be useful, just need to provide a way users can read a file to pass in to it)
            // Just to avoid bloatin this example to much, we will just add THIS program to its references, that way we don't need another
            // project to store the interfaces that both this class and the other uses. Just remember, this will expose ALL public classes to
            // the "script"
            options.ReferencedAssemblies.Add(Assembly.GetExecutingAssembly().Location);

            // Compile our code
            CompilerResults result;
            result = csProvider.CompileAssemblyFromSource(options, code);

            if (result.Errors.HasErrors)
            {
                // TODO: report back to the user that the script has errored
                return null;
            }

            if (result.Errors.HasWarnings)
            {
                // TODO: tell the user about the warnings, might want to prompt them if they want to continue
                // runnning the "script"
            }

            return result.CompiledAssembly;
        }

        static void RunScript(Assembly script)
        {
            // Now that we have a compiled script, lets run them
            foreach (Type type in script.GetExportedTypes())
            {
                foreach (Type iface in type.GetInterfaces())
                {
                    if (iface == typeof(ScriptingInterface.IScriptType1))
                    {
                        // yay, we found a script interface, lets create it and run it!

                        // Get the constructor for the current type
                        // you can also specify what creation parameter types you want to pass to it,
                        // so you could possibly pass in data it might need, or a class that it can use to query the host application
                        ConstructorInfo constructor = type.GetConstructor(System.Type.EmptyTypes);
                        if (constructor != null && constructor.IsPublic)
                        {
                            // lets be friendly and only do things legitimitely by only using valid constructors

                            // we specified that we wanted a constructor that doesn't take parameters, so don't pass parameters
                            ScriptingInterface.IScriptType1 scriptObject = constructor.Invoke(null) as ScriptingInterface.IScriptType1;
                            if (scriptObject != null)
                            {
                                //Lets run our script and display its results
                                MessageBox.Show(scriptObject.RunScript(50));
                            }
                            else
                            {
                                // hmmm, for some reason it didn't create the object
                                // this shouldn't happen, as we have been doing checks all along, but we should
                                // inform the user something bad has happened, and possibly request them to send
                                // you the script so you can debug this problem
                            }
                        }
                        else
                        {
                            // and even more friendly and explain that there was no valid constructor
                            // found and thats why this script object wasn't run
                        }
                    }
                }
            }
        }
    }
}


IronPython. Here's an overview of how to embed it.