Getting the fully qualified name of a type from a TypeInfo object

Question

Is it somehow possible to get the fully qualified name of the type contained in a TypeInfo object?

In the debugger many of these values nicely show up as

Answer 1

The ToDisplayString method lets you pass in a "format" object which has a huge number of options for controlling how you want to format stuff:

var symbolDisplayFormat = new SymbolDisplayFormat(
    typeQualificationStyle: SymbolDisplayTypeQualificationStyle.NameAndContainingTypesAndNamespaces);

string fullyQualifiedName = typeSymbol.ToDisplayString(symbolDisplayFormat);

The reason your getting keywords like "int" is the default format is including the SymbolDisplayMiscellaneousOptions.UseSpecialTypes flag which specifies to use the language keywords for special types vs. the regular name.

Answer 2

I couldn't find something built-in either and I'm quite sure this isn't the most elegant way, but it worked for me to construct a qualified type name like this:

private static string GetQualifiedTypeName(ISymbol symbol)
{
    return symbol.ContainingNamespace 
        + "." + symbol.Name 
        + ", " + symbol.ContainingAssembly;
}

If you don't need an assembly qualified type name don't concatenate ContainingAssembly at the end of the last line.

Answer 3

Using the semantic model you can also do it like i did it here:

var typeInfo = context.SemanticModel.GetTypeInfo(identifierNameSyntax);
var namedType = typeInfo.Type as INamedTypeSymbol;
if (namedType != null && namedType.Name == nameof(ConfiguredTaskAwaitable) && GetFullNamespace(namedType) == typeof(ConfiguredTaskAwaitable).Namespace)
    return true;

where "GetFullNamespace" works like this:

    public static IEnumerable<string> GetNamespaces(INamedTypeSymbol symbol)
    {
        var current = symbol.ContainingNamespace;
        while (current != null)
        {
            if (current.IsGlobalNamespace)
                break;
            yield return current.Name;
            current = current.ContainingNamespace;
        }
    }

    public static string GetFullNamespace(INamedTypeSymbol symbol)
    {
        return string.Join(".", GetNamespaces(symbol).Reverse());
    }

    public static string GetFullTypeName(INamedTypeSymbol symbol)
    {
        return string.Join(".", GetNamespaces(symbol).Reverse().Concat(new []{ symbol.Name }));
    }

Obviously Jason Malinowski's answer is more convenient for simple cases