Code listings for blog post about cache busting and long time caching. Read about it here: https://stefanolsen.com/posts/cache-busting-2-an-update-for-aspnet-core/

Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.Net.Http.Headers;

public class Startup
{
    public void Configure(IApplicationBuilder app)
    {
        var staticFileOptions = new StaticFileOptions
        {
            OnPrepareResponse = context =>
            {
                const int secondsInAYear = 365 * 24 * 60 * 60;
                context.Context.Response.Headers[HeaderNames.CacheControl] = $"public,maxAge={secondsInAYear}";
            }
        };
        app.UseStaticFiles(staticFileOptions);
    }
}

UrlHelperExtensions.cs

public static class UrlHelperExtensions
{
    private const string WebRootBasePath = "wwwroot";
    private static readonly ConcurrentDictionary<string, string> CachedFileHashes =
        new ConcurrentDictionary<string, string>();

    public static string ContentVersioned(this IUrlHelper urlHelper, string contentPath)
    {
        string url = urlHelper.Content(contentPath);

        // Check if we already cached the file hash in the cache. If not, add it using the inner method.
        string fileHash = CachedFileHashes.GetOrAdd(url, key =>
        {
            var fileInfo = new FileInfo(WebRootBasePath + key);

            // If file exists, generate a hash of it, otherwise return null.
            return fileInfo.Exists
                ? ComputeFileHash(fileInfo.OpenRead())
                : null;
        });

        return $"{url}?v={fileHash}";
    }

    private static string ComputeFileHash(Stream fileStream)
    {
        using (SHA256 hasher = new SHA256Managed())
        using (fileStream)
        {
            byte[] hashBytes = hasher.ComputeHash(fileStream);

            var sb = new StringBuilder(hashBytes.Length * 2);

            foreach (byte hashByte in hashBytes)
            {
                sb.AppendFormat("{0:x2}", hashByte);
            }

            return sb.ToString();
        }
    }
}