Question

我正在尝试在我的web项目中使用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 site上找到了一个示例（标题为 LESS，CoffeeScript，SCSS，Sass Bundling。）。这给了我一个LessTransform类看起来像这样：

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

和我的BundleConfig课程中的这一行：

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

最后我在_Layout.cshtml中的<head>中有以下行：

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

如果我的网站处于调试模式，则会将其呈现给浏览器：

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

应用.less文件中的规则，并在该链接后显示LESS已正确转换为CSS。

但是，如果我将网站置于发布模式，则会显示出来：

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

.less文件中的规则未已应用，因为链接后面的IIS会出现404错误。

所以捆绑似乎出现了问题。如何让它在发布模式下工作，或者如何找出确切的错误？

Answer 1

作为accepted answer的补充，我创建了一个LessBundle类，它是StyleBundle类的Less eqivalent。

LessBundle.cs 代码为：

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 BundleConfig.RegisterBundles（BundleCollection）方法中：

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

的更新

此方法在关闭优化时工作正常，但在启用优化时遇到了一些小问题（使用CSS资源路径）。经过一个小时的研究，我发现我有reinvented the wheel...

如果您想要我上面描述的LessBundle功能，请查看System.Web.Optimization.Less。

可以找到NuGet包here。

Answer 2

无点引擎似乎需要知道当前处理的bundle文件的路径以解析@import路径。如果您运行上面的进程代码，则当解析的.less文件导入的文件较少时，dotless.Core.Less.Parse（）的结果为空字符串。

Ben Foster在这里的回答将通过首先阅读导入的文件来解决这个问题：

Import Files and DotLess

按如下方式更改LessTransform文件：

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;
    }
}

Answer 3

接受的答案不适用于最近对ASP.NET的更改，因此不再正确。

我已在接受的答案中修改了来源：

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必须使用其完整路径，即您必须使用@import "~/Areas/Admin/Css/global.less";而不是@import "global.less";。

Answer 4

看起来这样有效 - 我更改了Process方法来迭代文件集：

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";
}

如果你的less文件中有任何@import语句，这会中断，在这种情况下你需要做更多的工作，如下所示：https://gist.github.com/chrisortman/2002958

Answer 5

已经有了一些很好的答案，这是我在尝试添加关注less文件的MVC包时找到的一个非常简单的解决方案。

创建less文件后（例如，test.less），右键单击该文件，然后在网络编译器（get it here）选项下，选择Compile File。

这将生成css文件中生成的less文件及其缩小版本。（test.css和test.min.css）。

在您的捆绑包上，只需参考生成的css文件

即可

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

bundles.Add(style);

在您的观点中，引用该捆绑包：

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

它应该可以正常工作。

如何使用ASP.Net MVC 4在发布模式下捆绑LESS文件？

5 个答案:

的更新