I know the answer (it's 42)

Code Generation in multiple languages

I'm currently working on a personal project that needs to spit out code after parsing some XML file. I had previously used the .NET frameworks CodeDom to do on the fly compilation and hence tried digging it up to see if I could use it for code generation. In a small time I was completely blown over by the feature set and what I could achieve in a relatively small time.

I had initially expected to get little support from the framework and had thought I'd manipulate text to generate the C# code. I now figured out that I could use the CodeDom to build the code structure hierarchy and just pass on a language parameter and if that language is supported generate code using that language. Suddenly my application was not limited to C# but I could use VB.NET or VJ# for my output code as well. To demonstrate this I'd skip the XML parsing (serialization and logic) part. The following code generates a hello world program in any of the supported .NET language

private void BtnGenerate_Click(object sender, EventArgs e)
{

    TextCode.Text  = GenerateCode("C#");
    TextCode.Text += GenerateCode("VJ#");
    TextCode.Text += GenerateCode("VB");
}
public string GenerateCode(string language)
{
    // get CodeDom provider from the language name
    CodeDomProvider provider =
            CSharpCodeProvider.CreateProvider(language);
    // generate the code 
    return GenerateCode(provider);
}


public string GenerateCode(CodeDomProvider provider)
{
    // open string based in memory streams 
    using(StringWriter writer = new StringWriter())
    using (IndentedTextWriter tw = 
        new IndentedTextWriter(writer, " "))
    {
        // create top level namespace
        CodeNamespace myNamespace = 
            new CodeNamespace("AbhinabaNameSpace");
        // create file level comment
        CodeComment comment = new CodeComment(
            string.Format("Generated on {0}",
                DateTime.Now.ToLocalTime().ToShortDateString()),
            false);
        CodeCommentStatement commentStatement =
            new CodeCommentStatement(comment);
        myNamespace.Comments.Add(commentStatement);
        // add using statements for the required namespaces
        myNamespace.Imports.Add(
            new CodeNamespaceImport("System"));
        // define the one and only class
        CodeTypeDeclaration mainClass = 
            new CodeTypeDeclaration();
        mainClass.IsClass = true;
        mainClass.Name = "HelloWorldMainClass";
        mainClass.Attributes = MemberAttributes.Public;
        myNamespace.Types.Add(mainClass);
        //define the entry point which'd be 
        //Main method in C#
        CodeEntryPointMethod mainMethod = 
            new CodeEntryPointMethod();
        mainMethod.Comments.Add(
            new CodeCommentStatement("<summary>", true));
        mainMethod.Comments.Add(
            new CodeCommentStatement("Entry point", true));
        mainMethod.Comments.Add(
            new CodeCommentStatement("</summary>", true));
        mainClass.Members.Add(mainMethod);
        //define the string variable message
        CodeVariableDeclarationStatement strDecl = 
            new CodeVariableDeclarationStatement(
                new CodeTypeReference(typeof(string)),
                "message");
        mainMethod.Statements.Add(strDecl);
        //create the message = "hello world" statement
        CodeAssignStatement ptxAssign = 
            new CodeAssignStatement(
                new CodeVariableReferenceExpression("message"),
                new CodeSnippetExpression("\"hello world\""));
        mainMethod.Statements.Add(ptxAssign);
        //call console.writeline to print the statement
        CodeMethodInvokeExpression invokeConsoleWriteLine =
            new CodeMethodInvokeExpression(
                new CodeTypeReferenceExpression(typeof(Console)), 
                "WriteLine",
                new CodeExpression[] 
                {
                    new CodeArgumentReferenceExpression(
                                                "message"),
                }
            );
        mainMethod.Statements.Add(invokeConsoleWriteLine);
        // code generation options
        CodeGeneratorOptions opt = new CodeGeneratorOptions();
        opt.BracingStyle = "C";
        opt.BlankLinesBetweenMembers = false;
        // generate the code and return it
        provider.GenerateCodeFromNamespace(myNamespace, tw, opt);
        return writer.ToString();
    }
}

If only more languages were on .NET I could build the list in http://www2.latech.edu/~acm/HelloWorld.shtml in about couple of hours :)

I get the following output

In C#
=======
// Generated on 2/27/2006
namespace AbhinabaNameSpace
{
    using System;
    
    public class HelloWorldMainClass
    {
        /// 

        /// Entry point
        /// 
        public static void Main()
        {
            string message;
            message = "hello world";
            System.Console.WriteLine(message);
        }
    }
}

VJ#
=======
// Generated on 2/27/2006
package AbhinabaNameSpace;
import System.*;

public class HelloWorldMainClass
{
    /** Entry point */
    public static void main(String[] args)
    {
        String message;
        message = "hello world";
        System.Console.WriteLine(message);
    }
}



VB
=======
Imports System

'Generated on 2/27/2006
Namespace AbhinabaNameSpace
    Public Class HelloWorldMainClass
        '''

        '''Entry point
        '''
        Public Shared Sub Main()
            Dim message As String
            message = "hello world"
            System.Console.WriteLine(message)
        End Sub
    End Class
End Namespace