Here’s the list of what’s new in this preview:

• New Razor features: @attribute, @code, @key, @namespace, markup in @functions
• Blazor directive attributes
• Authentication & authorization support for Blazor apps
• Static assets in Razor class libraries
• Json.NET no longer referenced in project templates
• Certificate and Kerberos Authentication
• SignalR Auto-reconnect
• Managed gRPC Client
• gRPC Client Factory
• gRPC Interceptors 

Here’s what’s new in this preview release:

• .NET Hot Reload updates for dotnet watch
• ASP.NET Core SPA templates updated to Angular 11 and React 17
• Use Razor syntax in SVG foreignObject elements
• Specify null for Action and RenderFragment component parameters
• Reduced Blazor WebAssembly download size with runtime relinking
• Configurable buffer threshold before writing to disk in Json.NET output formatter
• Subcategories for better filtering of Kestrel logs
• Faster get and set for HTTP headers
• Configurable unconsumed incoming buffer size for IIS 

using System.Web;

        bool IsInWeb
        {
            get
            {
                return HttpContext.Current != null;
            }
        }