25

我正在尝试在我的 Web 项目中包含 LESS 文件，并将 MVC 4 捆绑功能调用到 dotLess 库中以将 LESS 转换为 CSS，然后缩小结果并将其提供给浏览器。

我在ASP.NET 站点上找到了一个示例（在LESS、CoffeeScript、SCSS、Sass Bundling.标题下）。这给了我一个LessTransform看起来像这样的类：

public class LessTransform : IBundleTransform
{
    public void Process(BundleContext context, BundleResponse response)
    {
        response.Content = dotless.Core.Less.Parse(response.Content);
        response.ContentType = "text/css";
    }
}

BundleConfig我班上的这一行：

bundles.Add(new Bundle(
    "~/Content/lessTest", 
    new LessTransform(), 
    new CssMinify()).Include("~/Content/less/test.less"));

最后，我的 _Layout.cshtml 中有以下行<head>：

@Styles.Render("~/Content/lessTest")

如果我的站点处于调试模式，则会将其呈现给浏览器：

<link href="/Content/less/test.less" rel="stylesheet"/>

应用了 .less 文件中的规则，并且跟随该链接显示 LESS 已正确转换为 CSS。

但是，如果我将站点置于发布模式，则会呈现以下内容：

<link href="/Content/less?v=lEs-HID6XUz3s2qkJ35Lvnwwq677wTaIiry6fuX8gz01" rel="stylesheet"/>

.less 文件中的规则未应用，因为点击链接会从 IIS 中得到 404 错误。

因此，捆绑似乎出了点问题。我如何让它在发布模式下工作，或者我如何找出到底出了什么问题？

4

5 回答 5

15

作为已接受答案的补充，我创建了一个 LessBundle 类，它是 StyleBundle 类的 Less 等价物。

LessBundle.cs代码是：

using System.Web.Optimization;

namespace MyProject
{
    public class LessBundle : Bundle
    {
        public LessBundle(string virtualPath) : base(virtualPath, new IBundleTransform[] {new LessTransform(), new CssMinify()})
        {

        }

        public LessBundle(string virtualPath, string cdnPath)
            : base(virtualPath, cdnPath, new IBundleTransform[] { new LessTransform(), new CssMinify() })
        {

        }
    }
}

用法类似于 StyleBundle 类，指定 LESS 文件而不是 CSS 文件。

将以下内容添加到您的BundleConfig.RegisterBundles(BundleCollection)方法中：

bundles.Add(new LessBundle("~/Content/less").Include(
                 "~/Content/MyStyles.less"));

更新

此方法在关闭优化的情况下运行良好，但在打开优化时我遇到了一些小问题（使用 CSS 资源路径）。经过一个小时研究这个问题后，我发现我重新发明了轮子......

如果您确实需要我上面描述的 LessBundle 功能，请查看System.Web.Optimization.Less。

NuGet 包可在此处找到。

于 2013-12-20T12:28:40.563 回答
12

2019 年 12 月 8 日编辑这不再是这个问题的可接受答案，因为多年来 ASP.NET 发生了重大变化。后面还有其他答案修改了此代码或提供了其他答案来帮助您解决此问题。

似乎无点引擎需要知道当前处理的捆绑文件的路径才能解析 @import 路径。如果您运行上面的流程代码，当正在解析的 .less 文件导入了其他 less 文件时，dotless.Core.Less.Parse() 的结果是一个空字符串。

Ben Foster 的回复将通过首先读取导入的文件来解决此问题：

导入文件和 DotLess

更改您的 LessTransform 文件，如下所示：

public class LessTransform : IBundleTransform
{
    public void Process(BundleContext context, BundleResponse bundle)
    {
        if (context == null)
        {
            throw new ArgumentNullException("context");
        }

        if (bundle == null)
        {
            throw new ArgumentNullException("bundle");
        }

        context.HttpContext.Response.Cache.SetLastModifiedFromFileDependencies();

        var lessParser = new Parser();
        ILessEngine lessEngine = CreateLessEngine(lessParser);

        var content = new StringBuilder(bundle.Content.Length);

        var bundleFiles = new List<FileInfo>();

        foreach (var bundleFile in bundle.Files)
        {
            bundleFiles.Add(bundleFile);

            SetCurrentFilePath(lessParser, bundleFile.FullName);
            string source = File.ReadAllText(bundleFile.FullName);
            content.Append(lessEngine.TransformToCss(source, bundleFile.FullName));
            content.AppendLine();

            bundleFiles.AddRange(GetFileDependencies(lessParser));
        }

        if (BundleTable.EnableOptimizations)
        {
            // include imports in bundle files to register cache dependencies
            bundle.Files = bundleFiles.Distinct();
        }

        bundle.ContentType = "text/css";
        bundle.Content = content.ToString();
    }

    /// <summary>
    /// Creates an instance of LESS engine.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    private ILessEngine CreateLessEngine(Parser lessParser)
    {
        var logger = new AspNetTraceLogger(LogLevel.Debug, new Http());
        return new LessEngine(lessParser, logger, true, false);
    }

    /// <summary>
    /// Gets the file dependencies (@imports) of the LESS file being parsed.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    /// <returns>An array of file references to the dependent file references.</returns>
    private IEnumerable<FileInfo> GetFileDependencies(Parser lessParser)
    {
        IPathResolver pathResolver = GetPathResolver(lessParser);

        foreach (var importPath in lessParser.Importer.Imports)
        {
            yield return new FileInfo(pathResolver.GetFullPath(importPath));
        }

        lessParser.Importer.Imports.Clear();
    }

    /// <summary>
    /// Returns an <see cref="IPathResolver"/> instance used by the specified LESS lessParser.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    private IPathResolver GetPathResolver(Parser lessParser)
    {
        var importer = lessParser.Importer as Importer;
        var fileReader = importer.FileReader as FileReader;

        return fileReader.PathResolver;
    }

    /// <summary>
    /// Informs the LESS parser about the path to the currently processed file. 
    /// This is done by using a custom <see cref="IPathResolver"/> implementation.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    /// <param name="currentFilePath">The path to the currently processed file.</param>
    private void SetCurrentFilePath(Parser lessParser, string currentFilePath)
    {
        var importer = lessParser.Importer as Importer;

        if (importer == null)
            throw new InvalidOperationException("Unexpected dotless importer type.");

        var fileReader = importer.FileReader as FileReader;

        if (fileReader == null || !(fileReader.PathResolver is ImportedFilePathResolver))
        {
            fileReader = new FileReader(new ImportedFilePathResolver(currentFilePath));
            importer.FileReader = fileReader;
        }
    }
}

public class ImportedFilePathResolver : IPathResolver
{
    private string currentFileDirectory;
    private string currentFilePath;

    public ImportedFilePathResolver(string currentFilePath)
    {
        if (string.IsNullOrEmpty(currentFilePath))
        {
            throw new ArgumentNullException("currentFilePath");
        }

        CurrentFilePath = currentFilePath;
    }

    /// <summary>
    /// Gets or sets the path to the currently processed file.
    /// </summary>
    public string CurrentFilePath
    {
        get { return currentFilePath; }
        set
        {
            currentFilePath = value;
            currentFileDirectory = Path.GetDirectoryName(value);
        }
    }

    /// <summary>
    /// Returns the absolute path for the specified improted file path.
    /// </summary>
    /// <param name="filePath">The imported file path.</param>
    public string GetFullPath(string filePath)
    {
        if (filePath.StartsWith("~"))
        {
            filePath = VirtualPathUtility.ToAbsolute(filePath);
        }

        if (filePath.StartsWith("/"))
        {
            filePath = HostingEnvironment.MapPath(filePath);
        }
        else if (!Path.IsPathRooted(filePath))
        {
            filePath = Path.GetFullPath(Path.Combine(currentFileDirectory, filePath));
        }

        return filePath;
    }
}
于 2013-03-07T13:15:10.987 回答
3

接受的答案不适用于最近对 ASP.NET 的更改，因此不再正确。

我已经在接受的答案中修复了来源：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Web.Hosting;
using System.Web.Optimization;
using dotless.Core;
using dotless.Core.Abstractions;
using dotless.Core.Importers;
using dotless.Core.Input;
using dotless.Core.Loggers;
using dotless.Core.Parser;

namespace Web.App_Start.Bundles
{
    public class LessTransform : IBundleTransform
    {
        public void Process(BundleContext context, BundleResponse bundle)
        {
            if (context == null)
            {
                throw new ArgumentNullException("context");
            }

            if (bundle == null)
            {
                throw new ArgumentNullException("bundle");
            }

            context.HttpContext.Response.Cache.SetLastModifiedFromFileDependencies();

            var lessParser = new Parser();
            ILessEngine lessEngine = CreateLessEngine(lessParser);

            var content = new StringBuilder(bundle.Content.Length);

            var bundleFiles = new List<BundleFile>();

            foreach (var bundleFile in bundle.Files)
            {
                bundleFiles.Add(bundleFile);

                var name = context.HttpContext.Server.MapPath(bundleFile.VirtualFile.VirtualPath);
                SetCurrentFilePath(lessParser, name);
                using (var stream = bundleFile.VirtualFile.Open())
                using (var reader = new StreamReader(stream))
                {
                    string source = reader.ReadToEnd();
                    content.Append(lessEngine.TransformToCss(source, name));
                    content.AppendLine();
                }

                bundleFiles.AddRange(GetFileDependencies(lessParser));
            }

            if (BundleTable.EnableOptimizations)
            {
                // include imports in bundle files to register cache dependencies
                bundle.Files = bundleFiles.Distinct();
            }

            bundle.ContentType = "text/css";
            bundle.Content = content.ToString();
        }

        /// <summary>
        /// Creates an instance of LESS engine.
        /// </summary>
        /// <param name="lessParser">The LESS parser.</param>
        private ILessEngine CreateLessEngine(Parser lessParser)
        {
            var logger = new AspNetTraceLogger(LogLevel.Debug, new Http());
            return new LessEngine(lessParser, logger, true, false);
        }

        /// <summary>
        /// Gets the file dependencies (@imports) of the LESS file being parsed.
        /// </summary>
        /// <param name="lessParser">The LESS parser.</param>
        /// <returns>An array of file references to the dependent file references.</returns>
        private IEnumerable<BundleFile> GetFileDependencies(Parser lessParser)
        {
            IPathResolver pathResolver = GetPathResolver(lessParser);

            foreach (var importPath in lessParser.Importer.Imports)
            {
                yield return
                    new BundleFile(pathResolver.GetFullPath(importPath),
                        HostingEnvironment.VirtualPathProvider.GetFile(importPath));
            }

            lessParser.Importer.Imports.Clear();
        }

        /// <summary>
        /// Returns an <see cref="IPathResolver"/> instance used by the specified LESS lessParser.
        /// </summary>
        /// <param name="lessParser">The LESS parser.</param>
        private IPathResolver GetPathResolver(Parser lessParser)
        {
            var importer = lessParser.Importer as Importer;
            var fileReader = importer.FileReader as FileReader;

            return fileReader.PathResolver;
        }

        /// <summary>
        /// Informs the LESS parser about the path to the currently processed file. 
        /// This is done by using a custom <see cref="IPathResolver"/> implementation.
        /// </summary>
        /// <param name="lessParser">The LESS parser.</param>
        /// <param name="currentFilePath">The path to the currently processed file.</param>
        private void SetCurrentFilePath(Parser lessParser, string currentFilePath)
        {
            var importer = lessParser.Importer as Importer;

            if (importer == null)
                throw new InvalidOperationException("Unexpected dotless importer type.");

            var fileReader = importer.FileReader as FileReader;

            if (fileReader == null || !(fileReader.PathResolver is ImportedFilePathResolver))
            {
                fileReader = new FileReader(new ImportedFilePathResolver(currentFilePath));
                importer.FileReader = fileReader;
            }
        }
    }
}

请注意此代码的一个已知问题是 LESS @imports 必须使用它们的完整路径，即您必须使用@import "~/Areas/Admin/Css/global.less";而不是@import "global.less";.

于 2015-04-21T10:21:02.930 回答
2

看起来这样可行 - 我更改了Process迭代文件集合的方法：

public void Process(BundleContext context, BundleResponse response)
{
    var builder = new StringBuilder();
    foreach (var fileInfo in response.Files)
    {
        using (var reader = fileInfo.OpenText())
        {
            builder.Append(dotless.Core.Less.Parse(reader.ReadToEnd()));
        }
    }

    response.Content = builder.ToString();
    response.ContentType = "text/css";
}

如果您的 less 文件中有任何@import语句，则会中断，在这种情况下，您必须做更多的工作，如下所示：https ://gist.github.com/chrisortman/2002958

于 2013-03-06T18:58:51.527 回答
1

已经有一些很好的答案，这是我在尝试添加与文件有关的 MVC 包时为自己找到的一个非常简单的解决方案less。

创建less文件（例如test.less）后，右键单击它并在 Web 编译器（在此处获取）选项下选择Compile File.

css这会从您的文件生成结果文件less，以及它的缩小版本。（test.css和test.min.css）。

在您的捆绑包上，只需参考生成的css文件

style = new StyleBundle("~/bundles/myLess-styles")
    .Include("~/Content/css/test.css", new CssRewriteUrlTransform());

bundles.Add(style);

在您看来，请参考该捆绑包：

@Styles.Render("~/bundles/myLess-styles")

它应该可以正常工作。

于 2016-01-08T16:02:08.980 回答