c# - Sort and remove (unused) using statements Roslyn script/code?

Question

Sort and remove (unused) using statements Roslyn script/code? I'm looking for some .NET/Roslyn (compiler as service) code that can run through a project and sort and remove unused using statements. I believe this is possible with Roslyn? Can anyone point me to code that could do this rewrite?

Answer 1

This is a feature in Visual Studio, but academically I think you would collect using statements from your SyntaxTree like this:

var usings = syntaxTree.Root.DescendentNodes().Where(node is UsingDirectiveSyntax);

...and compare that to the namespaces resolved by the symbol table like this:

private static IEnumerable<INamespaceSymbol> GetNamespaceSymbol(ISymbol symbol)
{
    if (symbol != null && symbol.ContainingNamespace != null)
        yield return symbol.ContainingNamespace;
}

var ns = semanticModel.SyntaxTree.Root.DescendentNodes().SelectMany(node =>
    GetNamespaceSymbol(semanticModel.GetSemanticInfo(node).Symbol)).Distinct();