如何在Roslyn的类中查找未声明的变量？

Question

In Roslyn how do I find out if a private member variable is not used in class?

I have task that to comment any unused private variables. For example:

class Test
{
   private int I;// if it's not use then i need to comment it out.
}

Answer 1

Create semantic model and pass it to the Rewriter class constructor in Main method.

SemanticModel sm = Compilation.Create("StylecopImplementor")
    .AddReferences(MetadataReference.CreateAssemblyReference("mscorlib"))
    .AddSyntaxTrees(fileTree).GetSemanticModel(fileTree);

Rewriter syntaxwr = new Rewriter(sm);

I expose my semantic model to my Rewritter class.

class Rewriter : SyntaxRewriter
{
    SemanticModel model { get; set; }
    IEnumerable<Diagnostic> diagonists;

    public Rewriter(SemanticModel pModel)
    {
        model = pModel;             
        diagonists = pModel.GetDiagnostics();
    }
}

Then I use below code in VisitVariableDeclaration.

if (diagonists.Count() > 0)
{
    var diagitems = diagonists.Where(d => d.Info.MessageIdentifier.ToString().Equals("CS0168")).ToList();

    if (diagitems != null)
    {
        var ditem = diagitems.Where(d => d.Location.GetLineSpan(false).StartLinePosition.Line == node.GetLocation().GetLineSpan(false).StartLinePosition.Line).FirstOrDefault();

        if (ditem != null)
        {
            node = node.WithLeadingTrivia(Syntax.ParseTrailingTrivia("//"));                            
        }
    }
}

return base.VisitVariableDeclaration(node);

It will comment your variable declaration in your .cs file if it's not in use.

Answer 2

Compiler (as seen in VS.NET) will certainly issue a warning, you can get warnings from Roslyn too (found this ).

For deeper code analysis I'd suggest using more advanced tool, for example Phoenix compiler.