Skip to main content

How To Host Mono’s CSharp Compiler as a Service in .NET - For Runtime Code Evaluation/REPL

I Love C#Anders in his C# Futures Talk mentioned about C# Compiler as a Service and demonstrated an REPL (Read Evaluation Print Loop) implementation.

If this is going to be a part of C#/.NET framework, this will allow you to execute plain C# code strings during runtime. This will allow you to implement features like interactive scripting in your applications.

As of now, .NET/C# stack don’t have this. Enter Mono’s C# Compiler as a service implementation. Big Bang. Last April, Miguel announced the availability of Mono’s C# Compiler as a Service assembly, along with a neat REPL C# shell. From that point onwards, I was thinking about writing a quick post on some of my thoughts about hosting Mono’s assembly in your .NET applications, so here we go.

1 – Download the C# Shell and Mono.CSharp.dll assembly

A snapshot of the C# REPL shell and Mono.CSharp.dll is available from this direct link (From Miguel’s post). The Zip contains a C# REPL shell - csharp.exe – and also the Mono.CSharp.dll which is the Compiler as Service assembly that we may use to host the C# compiler in our .NET apps.

2 – Exploring Miguel’s C# REPL Shell

For now, fire up csharp.exe. Once you fire up the shell, type help; to get a list of Static methods available for meta purposes like showing the defined local variables (ShowVars), loading an assembly so that you can use the types inside the same (LoadAssembly) etc.

image 

Also, In the above screenshot of the console, you may see that I’m just assigning some value to variable ‘x’, and then printing it to the console.  Also, see this post from Miguel to learn what you can do more with the C# interactive shell - I know you’ve already fallen in love. Mono’s C# console supports {..} block syntax and some of kind of auto completion as well.

3 – Hosting Mono’s Compiler as a Service in your own .NET applications

Now, let us see how to host the Mono.CSharp.dll in your own .NET applications. Create a console application in Visual Studio, and Add a reference to Mono.CSharp.dll. Now, let us try some simple code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Mono.CSharp;

namespace MonoCompilerHost
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(">Mini Console\n\n");
            while (true) 
            {
                Console.Write(">"); 
                string input = Console.ReadLine();
                if (input == "@@") return;
                Evaluator.Run(input);
            }
        }
    }
}

In the code, you may see that we are importing the Mono.CSharp namespace, so that we can use the Evaluator class in the same. The Evaluator class has a 'Run' static method, that'll take some C# code as string, and execute the same. So, we just wrote a simple REPL leveraing Mono.CSharp.dll, which reads line by line C# code from the console and execute the same. Let us see our Mini Console app in action.

image

Note that our implementation is not very functional, it is just a ‘hello world’ application to demonstrate how to leverage Mono’s compiler as a service in your own .NET apps.

4 – Advanced Scenarios

There are quite a handful of useful scenarios where you can leverage runtime code evaluation/execution. Like, providing scripting features, allowing your users to write queries using LINQ or so, storing some logic in your application as non compiled, decoupled and plain C# code, that’ll be picked, compiled and executed by your system at run time etc etc. Will blog about that later.

Update: Read Second part of this article Dynamic Filtering and Querying in Your .NET applications - Using Mono’s C# Compiler As Service

You may also read some of my recent posts on 7 Free E-Books For .NET Programmers and Architects and Revisiting Few C# Concepts – Delegates, Anon methods, Expression Trees, Lambdas

Popular posts from this blog

Creating a quick Todo listing app on Windows using IIS7, Node.js and Mongodb

As I mentioned in my last post, more and more organizations are leaning towards Web Oriented Architecture (WOA) which are highly scalable. If you were exploring cool, scalable options to build highly performing web applications, you know what Node.js is for.After following the recent post from Scott Hanselman, I was up and running quickly with Node.js. In this post, I’ll explain step by step how I’ve setup Node.js and Mongodb to create a simple Todo listing application.Setting up Node.jsThis is what I’ve done.1 – Goto http://nodejs.org/, scroll down and download node.exe for Windows, and place it in your c:\node folder2 – Goto IIS Node project in Git at https://github.com/tjanczuk/iisnode, download the correct ‘retail’ link of IIS Node zip file (I downloaded the already built retail package, otherwise you can download and build from the source).3 – Extract the zip file some where, and run the install.bat or install_iisexpress.bat depending on your IIS Version. If you don’t have IIS in…

MVVM - Binding Multiple Radio Buttons To a single Enum Property in WPF

I had a property in my View Model, of an Enum type, and wanted to bind multiple radio buttons to this.

Firstly, I wrote a simple Enum to Bool converter, like this.

public class EnumToBoolConverter : IValueConverter { #region IValueConverter Members public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (parameter.Equals(value)) return true; else return false; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { return parameter; } #endregion }

And my enumeration is like

public enum CompanyTypes { Type1Comp, Type2Comp, Type3Comp } Now, in my XAML, I provided the enumeration as the ConverterParameter, of the Converter we wrote earlier, like
<Wi…

Top 7 Coding Standards & Guideline Documents For C#/.NET Developers

Some time back, I collated a list of 7 Must Read, Free EBooks for .NET Developers, and a lot of people found it useful. So, I thought about putting together a list of Coding Standard guidelines/checklists for .NET /C# developers as well.As you may already know, it is easy to come up with a document - the key is in implementing these standards in your organization, through methods like internal trainings, Peer Reviews, Check in policies, Automated code review tools etc. You can have a look at FxCop and/or StyleCop for automating the review process to some extent, and can customize the rules based on your requirements.Anyway, here is a list of some good Coding Standard Documents. They are useful not just from a review perspective - going through these documents can definitely help you and me to iron out few hidden glitches we might have in the programming portion of our brain. So, here we go, the listing is not in any specific order.1 – IDesign C# Coding StandardsIDesign C# coding stand…