ASP.NET Core Razor生成Html静态文件

一、前言

最近做项目的时候，使用Util进行开发，使用Razor写前端页面。初次使用感觉还是不大习惯，之前都是前后端分离的方式开发的，但是使用Util封装后的Angular后，感觉开发效率还是杠杠滴。

二、问题

在发布代码的时候，Webpack打包异常，提示是缺少了某些Html文件，我看了下相应的目录，发现目录缺少了部分Html文件，然后就问了何镇汐，给出的解决方案是，每个页面都需要访问一下才能生成相应的Html静态文件。这时候就产生了疑虑，是否有一种方式能获取所有路由，然后只需访问一次即可生成所有的Html页面。

三、解决方案

3.1 每次访问生成Html

解决方案思路：

继承ActionFilterAttribute特性，重写执行方法
访问的时候判断访问的Result是否ViewResult，如果是方可生成Html
从RazorViewEngine中查找到View后进行渲染

/// <summary>
/// 生成Html静态文件
/// </summary>
public class HtmlAttribute : ActionFilterAttribute {
    /// <summary>
    /// 生成路径，相对根路径，范例：/Typings/app/app.component.html
    /// </summary>
    public string Path { get; set; }

    /// <summary>
    /// 路径模板，范例：Typings/app/{area}/{controller}/{controller}-{action}.component.html
    /// </summary>
    public string Template { get; set; }

    /// <summary>
    /// 执行生成
    /// </summary>
    public override async Task OnResultExecutionAsync( ResultExecutingContext context, ResultExecutionDelegate next ) {
        await WriteViewToFileAsync( context );
        await base.OnResultExecutionAsync( context, next );
    }

    /// <summary>
    /// 将视图写入html文件
    /// </summary>
    private async Task WriteViewToFileAsync( ResultExecutingContext context ) {
        try {
            var html = await RenderToStringAsync( context );
            if( string.IsNullOrWhiteSpace( html ) )
                return;
            var path = Util.Helpers.Common.GetPhysicalPath( string.IsNullOrWhiteSpace( Path ) ? GetPath( context ) : Path );
            var directory = System.IO.Path.GetDirectoryName( path );
            if( string.IsNullOrWhiteSpace( directory ) )
                return;
            if( Directory.Exists( directory ) == false )
                Directory.CreateDirectory( directory );
            File.WriteAllText( path, html );
        }
        catch( Exception ex ) {
            ex.Log( Log.GetLog().Caption( "生成html静态文件失败" ) );
        }
    }

    /// <summary>
    /// 渲染视图
    /// </summary>
    protected async Task<string> RenderToStringAsync( ResultExecutingContext context ) {
        string viewName = "";
        object model = null;
        if( context.Result is ViewResult result ) {
            viewName = result.ViewName;
            viewName = string.IsNullOrWhiteSpace( viewName ) ? context.RouteData.Values["action"].SafeString() : viewName;
            model = result.Model;
        }
        var razorViewEngine = Ioc.Create<IRazorViewEngine>();
        var tempDataProvider = Ioc.Create<ITempDataProvider>();
        var serviceProvider = Ioc.Create<IServiceProvider>();
        var httpContext = new DefaultHttpContext { RequestServices = serviceProvider };
        var actionContext = new ActionContext( httpContext, context.RouteData, new ActionDescriptor() );
        using( var stringWriter = new StringWriter() ) {
            var viewResult = razorViewEngine.FindView( actionContext, viewName, true );
            if( viewResult.View == null )
                throw new ArgumentNullException( $"未找到视图： {viewName}" );
            var viewDictionary = new ViewDataDictionary( new EmptyModelMetadataProvider(), new ModelStateDictionary() ) { Model = model };
            var viewContext = new ViewContext( actionContext, viewResult.View, viewDictionary, new TempDataDictionary( actionContext.HttpContext, tempDataProvider ), stringWriter, new HtmlHelperOptions() );
            await viewResult.View.RenderAsync( viewContext );
            return stringWriter.ToString();
        }
    }

    /// <summary>
    /// 获取Html默认生成路径
    /// </summary>
    protected virtual string GetPath( ResultExecutingContext context ) {
        var area = context.RouteData.Values["area"].SafeString();
        var controller = context.RouteData.Values["controller"].SafeString();
        var action = context.RouteData.Values["action"].SafeString();
        var path = Template.Replace( "{area}", area ).Replace( "{controller}", controller ).Replace( "{action}", action );
        return path.ToLower();
    }
}

3.2 一次访问生成所有Html

解决方案思路：

获取所有已注册的路由
获取使用RazorHtml自定义特性的路由
忽略Api接口的路由
构建RouteData信息，用于在RazorViewEngine中查找到相应的视图
构建ViewContext用于渲染出Html字符串
将渲染得到的Html字符串写入文件

获取所有注册的路由，此处是比较重要的，其他地方也可以用到。

/// <summary>
/// 获取所有路由信息
/// </summary>
/// <returns></returns>
public IEnumerable<RouteInformation> GetAllRouteInformations()
{
    List<RouteInformation> list = new List<RouteInformation>();

    var actionDescriptors = this._actionDescriptorCollectionProvider.ActionDescriptors.Items;
    foreach (var actionDescriptor in actionDescriptors)
    {
        RouteInformation info = new RouteInformation();

        if (actionDescriptor.RouteValues.ContainsKey("area"))
        {
            info.AreaName = actionDescriptor.RouteValues["area"];
        }

        // Razor页面路径以及调用
        if (actionDescriptor is PageActionDescriptor pageActionDescriptor)
        {
            info.Path = pageActionDescriptor.ViewEnginePath;
            info.Invocation = pageActionDescriptor.RelativePath;
        }

        // 路由属性路径
        if (actionDescriptor.AttributeRouteInfo != null)
        {
            info.Path = $"/{actionDescriptor.AttributeRouteInfo.Template}";
        }

        // Controller/Action 的路径以及调用
        if (actionDescriptor is ControllerActionDescriptor controllerActionDescriptor)
        {
            if (info.Path.IsEmpty())
            {
                info.Path =
                    $"/{controllerActionDescriptor.ControllerName}/{controllerActionDescriptor.ActionName}";
            }

            var controllerHtmlAttribute = controllerActionDescriptor.ControllerTypeInfo.GetCustomAttribute<RazorHtmlAttribute>();

            if (controllerHtmlAttribute != null)
            {
                info.FilePath = controllerHtmlAttribute.Path;
                info.TemplatePath = controllerHtmlAttribute.Template;
            }

            var htmlAttribute = controllerActionDescriptor.MethodInfo.GetCustomAttribute<RazorHtmlAttribute>();

            if (htmlAttribute != null)
            {
                info.FilePath = htmlAttribute.Path;
                info.TemplatePath = htmlAttribute.Template;
            }

            info.ControllerName = controllerActionDescriptor.ControllerName;
            info.ActionName = controllerActionDescriptor.ActionName;
            info.Invocation = $"{controllerActionDescriptor.ControllerName}Controller.{controllerActionDescriptor.ActionName}";
        }

        info.Invocation += $"({actionDescriptor.DisplayName})";

        list.Add(info);
    }

    return list;
}

生成Html静态文件

/// <summary>
/// 生成Html文件
/// </summary>
/// <returns></returns>
public async Task Generate()
{
    foreach (var routeInformation in _routeAnalyzer.GetAllRouteInformations())
    {
        // 跳过API的处理
        if (routeInformation.Path.StartsWith("/api"))
        {
            continue;
        }
        await WriteViewToFileAsync(routeInformation);
    }
}

/// <summary>
/// 渲染视图为字符串
/// </summary>
/// <param name="info">路由信息</param>
/// <returns></returns>
public async Task<string> RenderToStringAsync(RouteInformation info)
{
    var razorViewEngine = Ioc.Create<IRazorViewEngine>();
    var tempDataProvider = Ioc.Create<ITempDataProvider>();
    var serviceProvider = Ioc.Create<IServiceProvider>();

    var routeData = new RouteData();
    if (!info.AreaName.IsEmpty())
    {
        routeData.Values.Add("area", info.AreaName);
    }

    if (!info.ControllerName.IsEmpty())
    {
        routeData.Values.Add("controller", info.ControllerName);
    }

    if (!info.ActionName.IsEmpty())
    {
        routeData.Values.Add("action", info.ActionName);
    }

    var httpContext = new DefaultHttpContext { RequestServices = serviceProvider };
    var actionContext = new ActionContext(httpContext, routeData, new ActionDescriptor());

    var viewResult = razorViewEngine.FindView(actionContext, info.ActionName, true);
    if (!viewResult.Success)
    {
        throw new InvalidOperationException($"找不到视图模板 {info.ActionName}");
    }

    using (var stringWriter = new StringWriter())
    {
        var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
        var viewContext = new ViewContext(actionContext, viewResult.View, viewDictionary, new TempDataDictionary(actionContext.HttpContext, tempDataProvider), stringWriter, new HtmlHelperOptions());
        await viewResult.View.RenderAsync(viewContext);
        return stringWriter.ToString();
    }
}

/// <summary>
/// 将视图写入文件
/// </summary>
/// <param name="info">路由信息</param>
/// <returns></returns>
public async Task WriteViewToFileAsync(RouteInformation info)
{
    try
    {
        var html = await RenderToStringAsync(info);
        if (string.IsNullOrWhiteSpace(html))
            return;

        var path = Utils.Helpers.Common.GetPhysicalPath(string.IsNullOrWhiteSpace(info.FilePath) ? GetPath(info) : info.FilePath);
        var directory = System.IO.Path.GetDirectoryName(path);
        if (string.IsNullOrWhiteSpace(directory))
            return;
        if (Directory.Exists(directory) == false)
            Directory.CreateDirectory(directory);
        File.WriteAllText(path, html);
    }
    catch (Exception ex)
    {
        ex.Log(Log.GetLog().Caption("生成html静态文件失败"));
    }
}

protected virtual string GetPath(RouteInformation info)
{
    var area = info.AreaName.SafeString();
    var controller = info.ControllerName.SafeString();
    var action = info.ActionName.SafeString();
    var path = info.TemplatePath.Replace("{area}", area).Replace("{controller}", controller).Replace("{action}", action);
    return path.ToLower();
}