PageModel静态化方案查找过很多资料。
基本上没找到一个使用视图引擎静态化PageModel的方案。
最终也只是解决了分部视图静态化方式，对于Layout也是无能为力。

以下实现了PageModel扩展实现了对视图渲染转换成Html。此方法不包含Layout和Section。

/// <summary>
/// 转换成Html
/// </summary>
/// <param name="pageModel"></param>
/// <param name="pageName"></param>
/// <returns></returns>
public async Task<string> ToHtml(this PageModel pageModel, string pageName)
{
    var actionContext = new ActionContext(
        pageModel.HttpContext,
        pageModel.RouteData,
        pageModel.PageContext.ActionDescriptor
    );
    using (var sw = new StringWriter())
    {
        IRazorViewEngine _razorViewEngine = pageModel.HttpContext.RequestServices.GetService(typeof(IRazorViewEngine)) as IRazorViewEngine;
        IRazorPageActivator _activator = pageModel.HttpContext.RequestServices.GetService(typeof(IRazorPageActivator)) as IRazorPageActivator;
        var result = _razorViewEngine.FindPage(actionContext, pageName);
        if (result.Page == null)
        {
            throw new ArgumentNullException($"The page {pageName} cannot be found.");
        }
        var page = result.Page;
        var view = new RazorView(_razorViewEngine,
            _activator,
            new List<IRazorPage>(),
            page,
            HtmlEncoder.Default,
            new DiagnosticListener("ViewRenderService"));
        var viewContext = new ViewContext(
            actionContext,
            view,
            pageModel.ViewData,
            pageModel.TempData,
            sw,
            new HtmlHelperOptions()
        );
        var pageNormal = ((Page)result.Page);
        pageNormal.PageContext = pageModel.PageContext;
        pageNormal.ViewContext = viewContext;
        _activator.Activate(pageNormal, viewContext);
        await page.ExecuteAsync();
        return sw.ToString();
    }
}

但是由于某些原因，我们需要生成包含layout的整个HTML页面，所以暂时没有别的办法，只能通过ActionFilter拦截的方式获取生成后的HTML，如下方代码

/// <summary>
/// Razor生成Html静态文件（保存目录为wwwroot）
/// </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
public class HtmlStaticAttribute : ActionFilterAttribute
{
    /// <summary>
    /// 路径模板，范例：static/{area}/{controller}/{action}.component.html
    /// </summary>
    public string Template { get; set; }
    /// <summary>
    /// 生成的最小间隔，单位（秒），比如设置5分钟，那么5分钟之内不会再生成
    /// </summary>
    public int MinInterval { get; set; } = 0;
    /// <summary>
    /// 结果执行之前 before
    /// </summary>
    /// <param name="context"></param>
    /// <param name="next"></param>
    /// <returns></returns>
    public override async Task OnResultExecutionAsync(ResultExecutingContext context, ResultExecutionDelegate next)
    {
        if ((context.Result is PageResult || context.Result is ViewResult) && IsBuildHtml(RouteReplace(context, Template)))
        {
            var response = context.HttpContext.Response;
            if (!response.Body.CanRead || !response.Body.CanSeek)
            {
                using (var ms = new MemoryStream())
                {
                    var old = response.Body;
                    response.Body = ms;
                    await base.OnResultExecutionAsync(context, next);
                    if (response.StatusCode == 200)
                    {
                        await WriteHtml(context, response.Body);
                    }
                    ms.Position = 0;
                    await ms.CopyToAsync(old);
                    response.Body = old;
                }
            }
            else
            {
                await base.OnResultExecutionAsync(context, next);
                var old = response.Body.Position;
                if (response.StatusCode == 200)
                {
                    await WriteHtml(context, response.Body);
                }
                response.Body.Position = old;
            }
        }
        else
        {
            await base.OnResultExecutionAsync(context, next);
        }
    }
    /// <summary>
    /// 根据路由参数进行模板替换
    /// </summary>
    /// <param name="context"></param>
    /// <param name="template">比如：static/{area}/{controller}/{action}/{id}.html</param>
    /// <returns></returns>
    public static string RouteReplace(ActionContext context, string template)
    {
        var path = template;
        foreach (var route in context.RouteData.Values)
            path = path.Replace("{" + route.Key + "}", route.Value.SafeString());
        return path.ToLower();
    }
    /// <summary>
    /// 根据条件判断是否允许生成HTML
    /// </summary>
    /// <param name="relativePath"></param>
    /// <returns></returns>
    protected bool IsBuildHtml(string relativePath)
    {
        if (MinInterval <= 0) return true;
        var path = Common.GetWebRootPath(relativePath);
        var fi = new FileInfo(path);
        if (!fi.Exists) return true;
        var time = fi.LastWriteTime.DateDiff(DateTime.Now);
        return time >= TimeSpan.FromSeconds(MinInterval);
    }
    /// <summary>
    /// 写HTML
    /// </summary>
    /// <param name="context"></param>
    /// <param name="stream"></param>
    protected async Task WriteHtml(ResultExecutingContext context, Stream stream)
    {
        stream.Position = 0;
        var responseReader = new StreamReader(stream);
        var responseContent = await responseReader.ReadToEndAsync();
        if (string.IsNullOrEmpty(responseContent)) return;
        var _logger = Web.GetService<ILogger<HtmlStaticAttribute>>();
        try
        {
            var path = Common.GetWebRootPath(RouteReplace(context, Template));
            FileHelper.Create(path, responseContent);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "生成html静态文件失败");
        }
    }
}

使用方法如下

//在页面顶部增加标签，只要访问该页面就会生成HTML
[HtmlStatic(MinInterval = 0, Template = "/static/{page}.html")]
public class IndexModel : PageModel
{
    public IndexModel()
    {
    }
}