c# - Get fully-qualified metadata name in Roslyn

Question

I need to get the full CLR name of a particular symbol. This means that for generic types I need the `1, `2, etc. appended to types. Now, ISymbol already has a property MetadataName which does exactly that. But it excludes surrounding types and namespaces, only giving the name of the symbol at hand.

The usual option for getting a fully-qualified name, i.e. via ToDisplayString doesn't quite work here because it will not use the MetadataName for its various parts.

Is there anything like this built-in? Or do I have to just concatenate the chain of ContainingSymbols with . in between? (And are there points where this assumption breaks down?)

EDIT: Just noticed that you need a + in between individual names if it's a type contained in another type, but apart from that, using . should work, I guess.

Answer 1

For now, having no better solution, I'm using the following:

public static string GetFullMetadataName(this ISymbol s) 
{
    if (s == null || IsRootNamespace(s))
    {
        return string.Empty;
    }

    var sb = new StringBuilder(s.MetadataName);
    var last = s;

    s = s.ContainingSymbol;

    while (!IsRootNamespace(s))
    {
        if (s is ITypeSymbol && last is ITypeSymbol)
        {
            sb.Insert(0, '+');
        }
        else
        {
            sb.Insert(0, '.');
        }

        sb.Insert(0, s.OriginalDefinition.ToDisplayString(SymbolDisplayFormat.MinimallyQualifiedFormat));
        //sb.Insert(0, s.MetadataName);
        s = s.ContainingSymbol;
    }

    return sb.ToString();
}

private static bool IsRootNamespace(ISymbol symbol) 
{
    INamespaceSymbol s = null;
    return ((s = symbol as INamespaceSymbol) != null) && s.IsGlobalNamespace;
}

which seems to work for now. Roslyn seems to have internal flags for SymbolDisplayFormat that enable that sort of thing (most notably SymbolDisplayCompilerInternalOptions.UseArityForGenericTypes, but not accessible to the outside.

Above code could probably be faster on recent .NET versions by using Append instead of Insert on the StringBuilder, but that's something to leave for profiling.