A markdig extension so add target blank to absolute urls

TargetLinkExtension.cs

public class TargetLinkExtension : IMarkdownExtension
        {

            public void Setup(MarkdownPipelineBuilder pipeline)
            {
            }

            public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
            {
                var htmlRenderer = renderer as HtmlRenderer;
                if (htmlRenderer != null)
                {
                    var inlineRenderer = htmlRenderer.ObjectRenderers.FindExact<LinkInlineRenderer>();
                    if (inlineRenderer != null)
                    {
                        inlineRenderer.TryWriters.Remove(TryLinkInlineRenderer);
                        inlineRenderer.TryWriters.Add(TryLinkInlineRenderer);
                    }
                }
            }

            private bool TryLinkInlineRenderer(HtmlRenderer renderer, LinkInline linkInline)
            {
                if (linkInline.Url == null)
                {
                    return false;
                }

                Uri uri;
                // Only process absolute Uri
                if (!Uri.TryCreate(linkInline.Url, UriKind.RelativeOrAbsolute, out uri) || !uri.IsAbsoluteUri)
                {
                    return false;
                }
                RenderTargetAttribute(uri, renderer, linkInline);
                return false;
            }

            private void RenderTargetAttribute(Uri uri, HtmlRenderer renderer, LinkInline linkInline)
            {

                linkInline.SetAttributes(new HtmlAttributes() { Properties = new List<KeyValuePair<string, string>>() { new KeyValuePair<string, string>("target", "_blank") } });

            }
        }

Add this for easy builder usage:

public static class MarkdownPipelineBuilderExtensions
    {
        public static MarkdownPipelineBuilder UseTargetLinkExtension(this MarkdownPipelineBuilder pipeline)
        {
            OrderedList<IMarkdownExtension> extensions;

            extensions = pipeline.Extensions;

            if (!extensions.Contains<TargetLinkExtension>())
            {
                extensions.Add(new TargetLinkExtension());
            }

            return pipeline;
        }
    }

new MarkdownPipelineBuilder()
            //...
            .UseTargetLinkExtension()
            .Build();