Scripted C# - or how to run dynamic C# code, without compilation

2012-04-14 Scripted C# - or how to run dynamic C# code, without compilation

As I started to develop small applications in C#, I thought why shouldn't I use the same paradigms that I used in Java... dynamic code execution, execution without compile/build/deploy process, hot-swap, etc.

I am far away from acomplishing the same functionality, but I started with writing a small program (81 lines) mentioned below.

When executing, it is able to compile and execute C# code that is written in text files, on the spot.

The mechanism is quite simple: it expects in the command line the name of an XML file (mentioned below this script) that describes:

the list of CS files that should be compiled;
the list of external binaries, if required;
the title of the application;
the entry point (the class name that contains the Main function).

An example (SMTPServer.csscript) of the input XML looks like attached.

Useful information:

the class mentioned in the CSScript/EntryClass node must have a Main(string[]args) method;
the Main method must be public and static!
additional parameters to be sent to the Main method are added to the executed command line!

Example of using the script attached.

In my development (that I started yesterday evening) I used some information from the following links:

http://msdn.microsoft.com/en-us/library/f02979c7.aspx - on how to parse integers and know if parsing was successful;
http://stackoverflow.com/questions/6167567/compile-multiple-code-files-into-an-assembly-with-net - on how to compile multiple files in only one assemble.

The application code is straight forward, and I don't think any comment is required. If you need any comment, then either you should learn programming, or study a bit some C-like languages.

If you wonder why I don't also give the EXE file, please feel free to open the Visual Studio, create an empty project, add a class and paste this code.

RunCS.cs

using System;
using System.CodeDom.Compiler;
using System.Reflection;
using System.Xml;
using System.Xml.XPath;
namespace CSScript {
    static class CSScript {
        static void Fatal(string message) {
            Console.WriteLine("FATAL: "+message);
            Console.ReadKey();
            Environment.Exit(1);
        }
        static private XPathNavigator config;
        [STAThread]
        static void Main(string[] args) {
            try {
                if(args.Length<1)
                    Fatal("Usage: CSScript <csscript_file> [<params>]");
                if(!System.IO.File.Exists(args[0]))
                    Fatal("e1204141741 - File '"+args[0]+"' does not exist");
                XmlDocument configXml=new XmlDocument();
                configXml.Load(args[0]);
                config=configXml.CreateNavigator();
                if(config.Select("CSScript/EntryClass").Count!=1)
                    Fatal("'EntryClass' must be one and only one");
                if(config.Select("CSScript/Title").Count!=1)
                    Fatal("'Title' must be one and only one");
                Assembly compiledScript=CompileCode();
                var title=config.SelectSingleNode("CSScript/Title");
                Console.WriteLine("Starting application '{0}'",title);
                Console.Title=title.ToString();
                string[] parameters=new string[args.Length-1];
                for(var i=1;i<args.Length;i++)
                    parameters[i-1]=args[i];
                if(compiledScript==null)
                    Fatal("e1204141028 - Application not compiled properly.");
                var entryClass=config.SelectSingleNode("CSScript/EntryClass").ToString();
                Type mainType=getMainType(compiledScript,entryClass);
                if(mainType==null)
                    Fatal("e1204141029 - Type "+entryClass+" could not be found");
                var mainMethod=mainType.GetMethod("Main");
                if(mainMethod==null)
                    Fatal("e1204141030 - Main Method 'Main' not found in class "+entryClass);
                mainMethod.Invoke(null,new string[][] { parameters });
                Console.Write("Press any key to exit...");
                Console.ReadKey();
            } catch(Exception e) {
                Fatal("e1204141747 - "+e.ToString());
            }
        }

        static Assembly CompileCode() {
            Microsoft.CSharp.CSharpCodeProvider csProvider=new Microsoft.CSharp.CSharpCodeProvider();
            CompilerParameters options=new CompilerParameters();
            options.GenerateExecutable=false;
            options.GenerateInMemory=true;
            options.ReferencedAssemblies.Add(Assembly.GetExecutingAssembly().Location);
            foreach(var assembly in config.Select("CSScript/ReferencedAssemblies/File"))
                options.ReferencedAssemblies.Add(assembly.ToString());
            var sources=config.Select("CSScript/CSSources/File");
            string[]files=new string[sources.Count];
            for(int i=0;i<files.Length;i++) {
                sources.MoveNext();
                files[i]=sources.Current.ToString();
            }
            CompilerResults results=csProvider.CompileAssemblyFromFile(options,files);
            if(results.Errors.HasErrors||results.Errors.HasWarnings)
                foreach(CompilerError error in results.Errors)
                    Console.WriteLine("COMPILATION "+(error.IsWarning?"WARNING":"ERROR")+": "+error.ToString()+": "+error.FileName+":"+error.Line+"@"+error.Column);
            if(results.Errors.HasErrors)
                Fatal("e1204141031 - Execution aborted, compilation generated errors!");
            return results.CompiledAssembly;
        }
        static Type getMainType(Assembly script,string typeFullName) {
            foreach(Type exportedType in script.GetExportedTypes())
                if(exportedType.FullName==typeFullName)
                    return exportedType;
            return null;
        }
    }
}

SMTPServer.csscript

<CSScript>
	<!-- this title should appear in the window's titlebar -->
	<Title>SMTPServer</Title>
	<!-- list of referenced assemblies - path might require updates for various computers -->
	<ReferencedAssemblies>
		<File>c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\System.dll</File>
		<File>c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\System.XML.dll</File>
	</ReferencedAssemblies>
	
	<!-- Entry class in syntax <namespace>.<class name> -->
	<!-- This class is expected to contain a Main method -->
	<EntryClass>SMTPServer.SMTPServer</EntryClass>

	<!-- The list of CS source files, relative to the application -->
	<CSSources>
		<File>csSources\Listener.cs</File>
		<File>csSources\MXDiscovery.cs</File>
		<File>csSources\Sender.cs</File>
		<File>csSources\SMTP.cs</File>
		<File>csSources\SMTPServer.cs</File>
	</CSSources>
</CSScript>

start.cmd

WARNING: Language not known: `cmd`

CSScript.exe SMTPServer.csscript listener-ip=0.0.0.0 listener-port=25