<our-cache vary-by-segment="true" />

[drpeck]

I'm using the partially support of Segments feature in Umbraco. As such I wish to vary some of my cached Razor by the segment. I've achieved this by implementing UmbracoCacheHelper with my own class. The class looks like this:

[HtmlTargetElement("my-cache")]
public class UmbracoCacheTagHelper : Our.Umbraco.TagHelpers.UmbracoCacheTagHelper
{
    private readonly IVariationContextAccessor _variationContextAccessor;

    public bool VaryBySegment { get; set; } = false;

    public UmbracoCacheTagHelper (
        CacheTagHelperMemoryCacheFactory factory, 
        HtmlEncoder htmlEncoder, 
        IUmbracoContextFactory umbracoContextFactory, 
        IUmbracoTagHelperCacheKeys cacheKeys,
        IVariationContextAccessor variationContextAccessor) :
        base(factory, htmlEncoder, umbracoContextFactory, cacheKeys)
    {
        _variationContextAccessor = variationContextAccessor;
    }

    public override async Task ProcessAsync (TagHelperContext context, TagHelperOutput output)
    {
        if (VaryBySegment)
        {
            var segment = _variationContextAccessor.VariationContext?.Segment;
            VaryBy = segment + VaryBy;
        }

        await base.ProcessAsync(context, output);
    }
}

I did try to look at how this might be done without using VaryBy, with the view to submitting a PR. Unfortunately I couldn't get my head around the cache keys. However I wondered cleverer then me might be able to achieve this.