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Posted 4 Oct 2007
Licenced CPOL

Script.NET a language for embedding scripting functionality into CLR Applications

, 16 Dec 2008
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Scripting language for .NET Framework 2.0. Supports native .NET Types, Dynamic casting, Meta programming.



New version of Script.NET was released. (13 June 2008)

It is now based on Irony Compiler Toolkit and has new run-time infrastructure.

Please use following link to download it: Download Latest Version.


Script .NET is a simple scripting engine which can be embedded into .NET framework applications to perform custom functionality in run-time. It works like VBA in Microsoft Office Applications. The difference is that Script .NET may use custom object model, different for each application. Script .NET is written in C#.

The key principles of Script .NET are:
  • Be simple
  • Be efficient
  • Be intuitive

The idea of Script .NET was born 17 September 2007. Then:
  • First alpha was released 03 October 2007.
  • 04 October – CodeProject Article submitted.
  • 21 October – WikiPedia article.
  • 19-20 Script.NET has been announced on Microsoft community forums and Google groups.
  • 22 October, CodePlex project had been launched.
  • 17 January 2008, DLR implementation of the language started.
  • 07 February 2008, The First working prototype of DLR MyL released.
  • 22 February 2008, Script.NET grammar was implemented with Irony. You can test it here.
  • 27 March 2008, Script.NET run-time was ported on Irony platform.

In current version I am using C# Compiler Tools from to produce Lexical analyzer and language parser.

Getting Started

All you need to start working with Script .NET is to add reference to ScriptDotNet.dll,

Example (in C# code):

using ScriptDotNet;<br />Script s = Script.Compile(<br />"MessageBox.Show('Hello .NET! This is Script .NET');");<br />s.AddType("MessageBox", typeof(MessageBox));<br />s.Execute();


For the sake of simplicity there are only four commonly known build-in types:

Type Name.NET AnalogueInitializer
doubledoublex = 1.23;
longlongx = 3;
stringstrings='Hello World!'
boolboolb = true
arrayobject[]A = [1, 1+2, 'Hello', s]

There is also implicit type object which is .NET object. All other types are derived from it. Script .NET supports type importing. Which means you can add any .NET Framework type to the Script .NET programs and work with it.

Note: If you haven’t added your time Script.NET run-time will search it in libraries loaded into current application domain. If the type was found then it will be cached for further use in Script Context.

Constant's declaration

Boolean = True | False
Object = null
String constants must be in '' brackets, example: s='Hello';


All variables in Script .NET are global and non-typed. They are stored in the Script Context. Script Context is a special structure which is used by Script Engine to store run-time information and interact with .NET.

However, function body creates local Contexts and store declared variables there. Functions have access to global variables.

Examples of variables:
X, x1, name_of_var.
Variables may be used in expressions, statements. The type information is computed in run-time.


The build-in arrays has a .NET type object[] and can store any values. The element of array may be accessed in a usual way: Array[index].


There is usual syntax of expressions, like:

X = (y+4)*2;
Y = a[5] + 8;
Z = Math.Sqrt(256);
P = new System.Drawing.Point(3,4);
'this is string' is string

Expressions have following operators:

+, -, *, / ,%, ! , | , & , != , > , < , is

There is also special operator new for creating instances of imported types.


A program in Script .NET is a sequence of statements. There are three usual statements: sequencing (;), loop, and branching.

If ... Then ... Else ...

if (Expression) statement else Statement


if (x>0) y = y + 1 ; else y = y – 1;
if (x>0) message = 'X is positive';

For ...

for (Expression1;Expression2;Expression3) Statement


for(i=0; i<10; i++) sum = sum + a[i];

Foreach ... in ...

foreach (Identifier in Expression) Statement

The result of Expression calculation must implement IEnumerable. Expression evaluates only once, before loop starts.


arr=[1,2,3,4,5]; sum = 0;
foreach(i in arr ) sum = sum + i;

While ...

while (Expression) Statement

while (i>0) i = i-1;


switch (expr){
case expr1: statement
default: statement

switch (i){
case 1: MessageBox.Show('Hello!');
case 2: MessageBox.Show('?');
default: MessageBox.Show('No way');

Break, Continue

Has usual meaning, may be used only inside the loop


Used only inside function call


function (id1, id2, ... , idn) {
Statement }

The function is creates local context during execution.

function fac(n){
if (n==1) return 1;
else return n*fac(n-1);

//pointer to a function
Func_pointer = fac;
Func_pointer(4); //Call function using pointer

Reserved functions

event – assign event to windows forms control
eval – evaluates value of an expression
clear – clears all variables in context

Script Context

Script Context is an object stores run-time information: variables and import types. Using Script Context you can add .NET objects to use in the script.

There are a number of functions:

  • Get the value of variable with name id within Context:
    public object Lookup(string id)
  • Add .NET object to the Script context with specified name
    public void AddObject(string name, object value)
  • Add .NET type to the script context to use it in new expressions
    public void AddType(string name, Type value)
  • Add build in object, which means you can invoke its Methods without specifying the name.
    public void AddBuildInObject (object object)
    In C# code (look example above)

    In Script.NET
    a = Pow(2,3); //Will call Math.Pow(2,3);
  • Removes build-in object
    public void RemoveBuildInObject (object object)
  • Gets the static field value
    public object GetStaticValue(string FullName)
    x = Context.GetStaticValue( 'double.NaN' );

Using .NET objects from Script.NET

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using ScriptDotNet;

namespace Test
    public partial class Form1 : Form
        public Form1()

        private void button1_Click(object sender, EventArgs e)

             Script s = Script.Compile(@"form.Text = 'Hello World'; 
               b = new Button()  ");

            s.AddObject("form", this);
            s.AddType("Button", typeof(Button));
            s.AddType("MessageBox", typeof(MessageBox));


Script.NET in .NET Applications

All you need to start working with Script .NET is to add reference to ScriptDotNet.dll,

using ScriptDotNet;
Script s = Script.Compile(
                 "MessageBox.Show('Hello .NET! This is Script .NET');");
s.AddType("MessageBox", typeof(MessageBox));

Script Test

Script Test is the application for testing Script.NET programs. You can use it to execute any scripting program and to observe results in Script Context.


Mutantic Framework

Mutantic Framework introduces a special kind of "meta" objects for working with objects of any type.

Definition: Mutant is a special object which could have all properties (fields, methods, etc), and may be converted to any type (or assigned to object of any type). The semantics of such conversion (or assignment) is pragmatically conditional, i.e. depends on user needs.

Example. Creation and Usage of MObject:

// Create Data Mutant Object
a = [ Text -> 'Hello from Mutant' ];
// Set Additional Fields
a.Top = 0;
a.Left = 0;
// Set corresponding fields of Windows Form object
// (Mutantic Assignment)
form := a;

Meta Programming

Script .NET has a special quotation operator: <[ program ]> which returns AST of a given program. The AST of the current program may be accessed with prog object.

Here is an example: Modification of current script

//Create an AST for MessageBox.Show('Hello'); program
ast = <[ MessageBox.Show('Hello'); ]>;
//Add this AST at the and of the current program

The <[ ... ]> operator and prog object allows Script.NET to generate new scripts or modify existing script at the run-time.

Alternative Solutions:

  • Java Script ActiveX control via COM interface
  • Lua via API
  • Python.NET native integration

External Links


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Petro Protsyk
Netherlands Netherlands
Please visit my website for more articles

I'm software developer & Ph.D. student

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