Handlebars DotNet Block Helper To String

Question

I have some legacy code I'm upgrading Handlebars dotnet on in which we were previously registering a block helper for usage as follows:

{upper}
  This will be up-cased
{/upper}

This was being done with the following helper method:

        private static void UpperHelper(TextWriter writer, HelperOptions options, dynamic context, params object[] parameters)
        {
            using (var stringWriter = new StringWriter())
            {
                options.Template(stringWriter, context);
                writer.Write(stringWriter.ToString().ToUpper());
            }
        }

However, with the new API we no longer can output to a TextWriter:

        private static void UpperHelper(EncodedTextWriter output, BlockHelperOptions options, Context context, Arguments arguments)
        {
            using (var stringWriter = new StringWriter())
            {
                // error - Cannot convert from StringWriter to EncodedTextWriter
                options.Template(stringWriter, context);
                output.Write(stringWriter.ToString().ToUpper());
            }
        }

I've tried everything I can think of to properly create an EncodedTextWriter targetting my stringWriter here, but no go.

I'd appreciate any help in getting this converted over. And while nowadays I wouldn't even register it as a block helper, there's templates in the wild I cannot control so I must keep it as a block helper.

Thanks

Answer 1

Took a bit of digging through the Handlebars.NET source to figure out how to initialize a EncodedTextWriter , but I managed to get this block helper functionality working.

var handlebarsContext = Handlebars.CreateSharedEnvironment();

handlebarsContext.RegisterHelper("upper", (output, options, context, parameters) =>
{
    var formatterProvider = new FormatterProvider(handlebarsContext.Configuration.FormatterProviders);
    using var writer = new EncodedTextWriter(
        ReusableStringWriter.Get(),
        handlebarsContext.Configuration.TextEncoder,
        formatterProvider);

    options.Template(writer, context);
    output.WriteSafeString(writer.ToString().ToUpper());
});

If you're using the global Handlebars context then the first line can be omitted and handlebarsContext can be replaced with Handlebars .