Accessing attribute info from DTE

Question

I have coded something like the following:

[Attrib(typeof(MyCustomType))]
public class TargetType
{
  // .....
}

I want to use EnvDTE

Answer 1

Is there an easier way to do this?

No, I don't think so, atleast for a <= VS2013, it seems that the CodeAttributeArgument doesn't go any further, which is shame. They should've released CodeAttributeArgument2 that has Value as CodeExpr :\..

If you use >=VS2014, you can get access to Roslyn, and it should become easier - don't know exactly how you can access roslyn inside VS extension, have to wait and see.

In order to get attributes, you can use VS helper:

public List<CodeElement> GetAllCodeElementsOfType(
    CodeElements elements, 
    vsCMElement elementType, 

    bool includeExternalTypes)
{
    var ret = new List<CodeElement>();

    foreach (CodeElement elem in elements)
    {
        // iterate all namespaces (even if they are external)
        // > they might contain project code
        if (elem.Kind == vsCMElement.vsCMElementNamespace)
        {
            ret.AddRange(
                GetAllCodeElementsOfType(
                    ((CodeNamespace)elem).Members, 
                    elementType, 
                    includeExternalTypes));
        }

        // if its not a namespace but external
        // > ignore it
        else if (elem.InfoLocation == vsCMInfoLocation.vsCMInfoLocationExternal && !includeExternalTypes)
            continue;

        // if its from the project
        // > check its members
        else if (elem.IsCodeType)
        {
            ret.AddRange(
                GetAllCodeElementsOfType(
                    ((CodeType)elem).Members, 
                    elementType, 
                    includeExternalTypes));
        }

        if (elem.Kind == elementType)
            ret.Add(elem);
    }
    return ret;
}

Original source: https://github.com/PombeirP/T4Factories/blob/master/T4Factories.Testbed/CodeTemplates/VisualStudioAutomationHelper.ttinclude

In a meanwhile, you could use backtracking solution, this is not nice, but it should work, haven't tested it exactly 100%. The basic idea is to start tracking backwards from the class, and keep track of different namespaces/usings that arein the path of a class. This tries to simulate pretty much what a real compiler would do, if it's going to resolve a type:

 var solution = (Solution2) _applicationObject.Solution;
var projects = solution.Projects;
var activeProject = projects
    .OfType<Project>()
    .First();

// locate my class.
var myClass = GetAllCodeElementsOfType(
    activeProject.CodeModel.CodeElements,
    vsCMElement.vsCMElementClass, false)
    .OfType<CodeClass2>()
    .First(x => x.Name == "Program");

// locate my attribute on class.
var mySpecialAttrib = myClass
    .Attributes
    .OfType<CodeAttribute2>()
    .First();



var attributeArgument = mySpecialAttrib.Arguments
    .OfType<CodeAttributeArgument>()
    .First();

string myType = Regex.Replace(
    attributeArgument.Value, // typeof(MyType)
    "^typeof.*\\((.*)\\)$", "$1"); // MyType*/

var codeNamespace = myClass.Namespace;
var classNamespaces = new List<string>();

while (codeNamespace != null)
{
    var codeNs = codeNamespace;
    var namespaceName = codeNs.FullName;

    var foundNamespaces = new List<string> {namespaceName};

    // generate namespaces from usings.
    var @usings = codeNs.Children
        .OfType<CodeImport>()
        .Select(x =>
            new[]
            {
                x.Namespace,
                namespaceName + "." + x.Namespace
            })
        .SelectMany(x => x)
        .ToList();

    foundNamespaces.AddRange(@usings);

    // prepend all namespaces:
    var extra = (
        from ns2 in classNamespaces
        from ns1 in @usings
        select ns1 + "." + ns2)
        .ToList();

    classNamespaces.AddRange(foundNamespaces);
    classNamespaces.AddRange(extra);

    codeNamespace = codeNs.Parent as CodeNamespace;
    if (codeNamespace == null)
    {
        var codeModel = codeNs.Parent as FileCodeModel2;
        if (codeModel == null) return;

        var elems = codeModel.CodeElements;
        if (elems == null) continue;

        var @extraUsings = elems
            .OfType<CodeImport>()
            .Select(x => x.Namespace);

        classNamespaces.AddRange(@extraUsings);
    }
}

// resolve to a type!
var typeLocator = new EnvDTETypeLocator();
var resolvedType = classNamespaces.Select(type =>
        typeLocator.FindTypeExactMatch(activeProject, type + "." + myType))
    .FirstOrDefault(type => type != null);

You need EnvDTETypeLocator too.

For VS2015, an example of roslyn integration can be found from here: https://github.com/tomasr/roslyn-colorizer/blob/master/RoslynColorizer/RoslynColorizer.cs

It'll definitely be A lot easier than it is with current CodeModel.

Answer 2

You can try to use a way described Get all methods that are decorated with a specific attribute using T4/EnvDTE