How to examine code and write a class with EnvDTE

Further to my experiments with the Guidance Automation Toolkit, I've been playing with generating code with my custom guidance package. Looking at the Service Factory GAT that's been released by the Patterns and Practices group, they use three different techniques for code generation; T4 templates, EnvDTE and CodeDom. If they use all three, I wondered which one I should be using. I've previously used the CodeDom in other projects and although it's very powerfull, you use it to generate the syntactic structure of the code and can then generate C#, VB or whatever, it is really long winded. T4 templates are at the opposite end of the spectrum, a bit like asp for code generation, you simply write a template of the code you want to generate and put code between <# #> marks that the template engine runs. The problem with it at the moment is that they are really new and the tools are there yet. There's no intellisense or code coloring for it and debugging isn't easy either.

So I decided to have a look at the EnvDTE Visual Studio automation class library for code generation. A lot of the GAT stuff seems to be built around it, so it's a natural fit for code generation duties. Unfortunately the documentation isn't that great, and this little demo of how to navigate a code file and write a class took much longer than it should have. But here it is, It gets the current visual studio environment and enumerates though all the projects and project items. It then examines itself outputting all the code elements and finally writes a new class inside its own namespace. If you try this out, make sure you name the file it's in 'HowToUseCodeModelSpike.cs'.

using System;
using NUnit.Framework;
using EnvDTE;
using EnvDTE80;

namespace Mike.Tests
{
    [TestFixture]
    public class DteSpike
    {
        [Test]
        public void HowToUseCodeModelSpike()
        {
            // get the DTE reference...
            DTE2 dte2 = (EnvDTE80.DTE2)System.Runtime.InteropServices.Marshal.GetActiveObject("VisualStudio.DTE.8.0");

            // get the solution
            Solution solution = dte2.Solution;
            Console.WriteLine(solution.FullName);

            // get all the projects
            foreach(Project project in solution.Projects)
            {
                Console.WriteLine("\t{0}", project.FullName);

                // get all the items in each project
                foreach(ProjectItem item in project.ProjectItems)
                {
                    Console.WriteLine("\t\t{0}", item.Name);

                    // find this file and examine it
                    if(item.Name == "HowToUseCodeModelSpike.cs")
                    {
                        ExamineItem(item);
                    }
                }
            }
        }

        // examine an item
        private void ExamineItem(ProjectItem item)
        {
            FileCodeModel2 model = (FileCodeModel2)item.FileCodeModel;
            foreach(CodeElement codeElement in model.CodeElements)
            {
                ExamineCodeElement(codeElement, 3);
            }
        }

        // recursively examine code elements
        private void ExamineCodeElement(CodeElement codeElement, int tabs)
        {
            tabs++;
            try
            {
                Console.WriteLine(new string('\t', tabs) + "{0} {1}", 
                    codeElement.Name, codeElement.Kind.ToString());

                // if this is a namespace, add a class to it.
                if(codeElement.Kind == vsCMElement.vsCMElementNamespace)
                {
                    AddClassToNamespace((CodeNamespace)codeElement);
                }

                foreach(CodeElement childElement in codeElement.Children)
                {
                    ExamineCodeElement(childElement, tabs);
                }
            }
            catch
            {
                Console.WriteLine(new string('\t', tabs) + "codeElement without name: {0}", codeElement.Kind.ToString());
            }
        }

        // add a class to the given namespace
        private void AddClassToNamespace(CodeNamespace ns)
        {
            // add a class
            CodeClass2 chess = (CodeClass2)ns.AddClass("Chess", -1, null, null, vsCMAccess.vsCMAccessPublic);
            
            // add a function with a parameter and a comment
            CodeFunction2 move = (CodeFunction2)chess.AddFunction("Move", vsCMFunction.vsCMFunctionFunction, "int", -1, vsCMAccess.vsCMAccessPublic, null);
            move.AddParameter("IsOK", "bool", -1);
            move.Comment = "This is the move function";

            // add some text to the body of the function
            EditPoint2 editPoint = (EditPoint2)move.GetStartPoint(vsCMPart.vsCMPartBody).CreateEditPoint();
            editPoint.Indent(null, 0);
            editPoint.Insert("int a = 1;");
            editPoint.InsertNewLine(1);
            editPoint.Indent(null, 3);
            editPoint.Insert("int b = 3;");
            editPoint.InsertNewLine(2);
            editPoint.Indent(null, 3);
            editPoint.Insert("return a + b; //");
        }
    }
}