If you mean the premium C#/VB languages in our .NET Languages Add-on, our CSharpQuickInfoProvider effectively does this kind of thing:
var context = new CSharpContextFactory().CreateContext(new TextSnapshotOffset(view.CurrentSnapshot, offset));
var resultSet = dotNetContext.Resolve();
Then we look at the top result in the result set, which could be an INamespaceResolverResult, ITypeResolverResult, ITypeMemberResolverResult, IParameterResolverResult, or IVariableResolverResult. The type references in those various results should be fully-qualified if we were able to resolve the type names.