Question

I’m interested to know who uses JScript.Net and for what sort of applications.
Whenever I’m reading MSDN .Net documentation, I always notice the JScript samples but in all the years I’ve been a C# dev I’ve never actually known anyone to use it.

What sort of applications are people using this for, and how does it measure, in terms of flexibility, power and general usage, to C#?

[Edit: Just to clarify – I’m not asking what JScript.Net is, I’m asking what people are actually using it for – i.e. interested to know actual usage scenarios and how people have found it to work with]

Answer 1

Rob – I have used JScript.NET in anger in one place in my code, which is essentially to expose the functionality of its eval method. Here is a cut-down version:

static public class Evaluator
{
    private const string _jscriptSource =
        @"package Evaluator
        {
           class Evaluator
           {
              public function Eval(expr : String) : String 
              { 
                 return eval(expr); 
              }
           }
        }";

    static private object _evaluator;
    static private Type _evaluatorType;

    static Evaluator()
    {
        InstantiateInternalEvaluator();
    }

    static private void InstantiateInternalEvaluator()
    {
        JScriptCodeProvider compiler = new JScriptCodeProvider();

        CompilerParameters parameters;
        parameters = new CompilerParameters();
        parameters.GenerateInMemory = true;

        CompilerResults results;
        results = compiler.CompileAssemblyFromSource(parameters, _jscriptSource);

        Assembly assembly = results.CompiledAssembly;
        _evaluatorType = assembly.GetType("Evaluator.Evaluator");

        _evaluator = Activator.CreateInstance(_evaluatorType);
    }

    static public object EvaluateToObject(string statement)
    {
        try
        {
            return _evaluatorType.InvokeMember(
                "Eval",
                BindingFlags.InvokeMethod,
                null,
                _evaluator,
                new object[] {statement}
                );
        }
        catch (Exception)
        {
            InstantiateInternalEvaluator();
            return null;
        }
    }

You can obviously create overloads for other return types. I can’t claim the original idea for this was mine! Uses for this would be, for example, to evaluate a string expression like 3 + 4 to 7 without expression parsing.