Mono.CSharp: how do I inject a value/entity *into* a script? - mono

Question

Just came across the latest build of Mono.CSharp and love the promise it offers.
Was able to get the following all worked out:
namespace XAct.Spikes.Duo
{
class Program
{
static void Main(string[] args)
{
CompilerSettings compilerSettings = new CompilerSettings();
compilerSettings.LoadDefaultReferences = true;
Report report = new Report(new Mono.CSharp.ConsoleReportPrinter());
Mono.CSharp.Evaluator e;
e= new Evaluator(compilerSettings, report);
//IMPORTANT:This has to be put before you include references to any assemblies
//our you;ll get a stream of errors:
e.Run("using System;");
//IMPORTANT:You have to reference the assemblies your code references...
//...including this one:
e.Run("using XAct.Spikes.Duo;");
//Go crazy -- although that takes time:
//foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
//{
// e.ReferenceAssembly(assembly);
//}
//More appropriate in most cases:
e.ReferenceAssembly((typeof(A).Assembly));
//Exception due to no semicolon
//e.Run("var a = 1+3");
//Doesn't set anything:
//e.Run("a = 1+3;");
//Works:
//e.ReferenceAssembly(typeof(A).Assembly);
e.Run("var a = 1+3;");
e.Run("A x = new A{Name=\"Joe\"};");
var a = e.Evaluate("a;");
var x = e.Evaluate("x;");
//Not extremely useful:
string check = e.GetVars();
//Note that you have to type it:
Console.WriteLine(((A) x).Name);
e = new Evaluator(compilerSettings, report);
var b = e.Evaluate("a;");
}
}
public class A
{
public string Name { get; set; }
}
}
And that was fun...can create a variable in the script's scope, and export the value.
There's just one last thing to figure out... how can I get a value in (eg, a domain entity that I want to apply a Rule script on), without using a static (am thinking of using this in a web app)?
I've seen the use compiled delegates -- but that was for the previous version of Mono.CSharp, and it doesn't seem to work any longer.
Anybody have a suggestion on how to do this with the current version?
Thanks very much.
References:
* Injecting a variable into the Mono.CSharp.Evaluator (runtime compiling a LINQ query from string)
* http://naveensrinivasan.com/tag/mono/

Answer 1

I know it's almost 9 years later, but I think I found a viable solution to inject local variables. It is using a static variable but can still be used by multiple evaluators without collision.
You can use a static Dictionary<string, object> which holds the reference to be injected. Let's say we are doing all this from within our class CsharpConsole:
public class CsharpConsole {
public static Dictionary<string, object> InjectionRepository {get; set; } = new Dictionary<string, object>();
}
The idea is to temporarily place the value in there with a GUID as key so there won't be any conflict between multiple evaluator instances. To inject do this:
public void InjectLocal(string name, object value, string type=null) {
var id = Guid.NewGuid().ToString();
InjectionRepository[id] = value;
type = type ?? value.GetType().FullName;
// note for generic or nested types value.GetType().FullName won't return a compilable type string, so you have to set the type parameter manually
var success = _evaluator.Run($"var {name} = ({type})MyNamespace.CsharpConsole.InjectionRepository[\"{id}\"];");
// clean it up to avoid memory leak
InjectionRepository.Remove(id);
}
Also for accessing local variables there is a workaround using Reflection so you can have a nice [] accessor with get and set:
public object this[string variable]
{
get
{
FieldInfo fieldInfo = typeof(Evaluator).GetField("fields", BindingFlags.NonPublic | BindingFlags.Instance);
if (fieldInfo != null)
{
var fields = fieldInfo.GetValue(_evaluator) as Dictionary<string, Tuple<FieldSpec, FieldInfo>>;
if (fields != null)
{
if (fields.TryGetValue(variable, out var tuple) && tuple != null)
{
var value = tuple.Item2.GetValue(_evaluator);
return value;
}
}
}
return null;
}
set
{
InjectLocal(variable, value);
}
}
Using this trick, you can even inject delegates and functions that your evaluated code can call from within the script. For instance, I inject a print function which my code can call to ouput something to the gui console window:
public delegate void PrintFunc(params object[] o);
public void puts(params object[] o)
{
// call the OnPrint event to redirect the output to gui console
if (OnPrint!=null)
OnPrint(string.Join("", o.Select(x => (x ?? "null").ToString() + "\n").ToArray()));
}
This puts function can now be easily injected like this:
InjectLocal("puts", (PrintFunc)puts, "CsInterpreter2.PrintFunc");
And just be called from within your scripts:
puts(new object[] { "hello", "world!" });
Note, there is also a native function print but it directly writes to STDOUT and redirecting individual output from multiple console windows is not possible.