将T4模板输出复制到新文件

Question

我正在尝试使用T4模板，使为我们的系统生成迁移稍微容易一些。有一件事我不太清楚（这让我怀疑我是否在使用T4模板），那就是如何将渲染的输出复制到一个新文件中。我可以手动创建一个文件并复制生成的文件的内容，但这有点违背我在这里的整个"让事情变得更容易"的精神。

这是我的模板。在渲染时，理想情况下会将其复制到同一目录中的"62 CreateWidgetsTable.cs"中。目标是有一个我现在可以编辑的文件（换句话说，我正在生成一个模板，而不是生成完整的文件。）如果我可以在VS中重命名生成的文件（然后让t4生成一个新的模板，它会一直放在那里，直到有人来使用它），那就足够了。

  <#@ template debug="false" hostspecific="false" language="C#" #>
  <#@ output extension=".cs" #>
  <#
    var migrationNumber = "62";
    var migrationName = "CreateWidgetsTable";
  #>
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using Migrator.Framework;
  namespace WidgetsIntl.Console.Migrations
  {
    [Migration(<#= DateTime.UtcNow.ToString("yyyyMMddhhmmss") #>)]
    public class _<#= migrationNumber  #>_<#= migrationName #> : Migration
    {
      public override void Up()
      {
      }
      public override void Down()
      {
      }
    }
  }

Answer 1

好吧，我找到了几种方法。最简单的方法是：t4将输出附加到现有文件中。关键信息是GenerationEnvironment是一个StringBuilder，它包含运行模板的结果，所以您可以将该结果写入任何您想要的旧文件！

另一种方法是使用T4工具箱。去下载吧！

然后，您可以制作一个模板，创建一个扩展Template（由T4工具箱定义）的类，该类覆盖一些默认行为：

<#@ template language="C#" hostspecific="True" debug="True" #>
<#@ include file="T4Toolbox.tt" #>
<#
    // make an instance of the class we define below, set some variables, and render it
    var tpl = new MyT4();
    tpl.MyVar = "Do those things you do";
    tpl.Render();
#>
<#+
public class MyT4 : Template 
{
    public MyVar = "some stuff";
    public override string TransformText()
    {
        Output.PreserveExistingFile = true; // tells T4 that you want to manually edit this file afterward (for scaffoling, which was my use case)
        Output.File = MyVar + ".cs"; // output will go in "some stuff.cs"
        /******************
        Template is defined here!
        *******************/
    #>
    public class <#=myVar.Replace(" ", "_") #> 
    { 
        public void Method()
        {
            return "Hi, I am <#= myvar #>";
        }
    }
    <#+
        /*************************
        now finishing up the TransformText() method
        *************************/
        return GenerationEnvironment.ToString();
    }
}
#>

Answer 2

在一些项目中，我使用allready下面的FileManager类。这是一个基于这篇博客文章的定制实现：http://damieng.com/blog/2009/11/06/multiple-outputs-from-t4-made-easy-revisited

<#@ assembly name="System.Core"
#><#@ assembly name="System.Data.Linq"
#><#@ assembly name="EnvDTE"
#><#@ assembly name="System.Xml"
#><#@ assembly name="System.Xml.Linq"
#><#@ import namespace="System"
#><#@ import namespace="System.CodeDom"
#><#@ import namespace="System.CodeDom.Compiler"
#><#@ import namespace="System.Collections.Generic"
#><#@ import namespace="System.Data.Linq"
#><#@ import namespace="System.Data.Linq.Mapping"
#><#@ import namespace="System.IO"
#><#@ import namespace="System.Linq"
#><#@ import namespace="System.Reflection"
#><#@ import namespace="System.Text"
#><#@ import namespace="System.Xml.Linq"
#><#@ import namespace="Microsoft.VisualStudio.TextTemplating"
#><#+
// Manager class records the various blocks so it can split them up
protected abstract class FileManager {
    protected FileManager(ITextTemplatingEngineHost host, StringBuilder template)
    {
        this.host = host;
        this.template = template;
    }
    protected abstract void CreateFile(String fileName, String content);
    public abstract String GetCustomToolNamespace(String fileName);
    public abstract String DefaultProjectNamespace { get; }
    public abstract void Process();
    public static FileManager Create(ITextTemplatingEngineHost host, StringBuilder template) 
    {
        return new VSManager(host, template);
    }
    protected class Block
    {
        public String Name;
        public int Start, Length;
    }
    protected Block currentBlock;
    protected List<Block> files = new List<Block>();
    protected Block footer = new Block();
    protected Block header = new Block();
    protected ITextTemplatingEngineHost host;
    protected StringBuilder template;
    public void StartNewFile(String name) 
    {
        if (name == null)
            throw new ArgumentNullException("name");
        CurrentBlock = new Block { Name = name };
    }
    public void StartFooter() {
        CurrentBlock = footer;
    }
    public void StartHeader() {
        CurrentBlock = header;
    }
    public void EndBlock() {
        if (CurrentBlock == null)
            return;
        CurrentBlock.Length = template.Length - CurrentBlock.Start;
        if (CurrentBlock != header && CurrentBlock != footer)
            files.Add(CurrentBlock);
        currentBlock = null;
    }
    protected bool IsFileContentDifferent(String fileName, String newContent) 
    {
        return !(File.Exists(fileName) && File.ReadAllText(fileName) == newContent);
    }
    protected Block CurrentBlock 
    {
        get { return currentBlock; }
        set {
            if (CurrentBlock != null)
                EndBlock();
            if (value != null)
                value.Start = template.Length;
            currentBlock = value;
        }
    }
    // VS Manager
    private class VSManager: FileManager 
    {
        private EnvDTE.ProjectItem templateProjectItem;
        private EnvDTE.DTE dte;
        private List<string> generatedFileNames = new List<string>();
        public override String DefaultProjectNamespace 
        {
            get 
            {
                return templateProjectItem.ContainingProject.Properties.Item("DefaultNamespace").Value.ToString();
            }
        }
        public override String GetCustomToolNamespace(string fileName) 
        {
            return dte.Solution.FindProjectItem(fileName).Properties.Item("CustomToolNamespace").Value.ToString();
        }
        public override void Process() 
        {           
            EndBlock();
            String headerText = template.ToString(header.Start, header.Length);
            String footerText = template.ToString(footer.Start, footer.Length);
            Directory.SetCurrentDirectory(Path.GetDirectoryName(host.TemplateFile));
            files.Reverse();
            foreach(Block block in files) 
            {
                String fileName = Path.GetFullPath(block.Name);
                String content = headerText + template.ToString(block.Start, block.Length) + footerText;
                generatedFileNames.Add(fileName);
                CreateFile(fileName, content);
                template.Remove(block.Start, block.Length);
            }
            this.ProjectSync(generatedFileNames);
            this.files = new List<Block>();
            this.footer = new Block();
            this.header = new Block();
            this.generatedFileNames = new List<string>();
        }
        protected override void CreateFile(String fileName, String content)
        {
            if (IsFileContentDifferent(fileName, content)) 
            {
                CheckoutFileIfRequired(fileName);
                File.WriteAllText(fileName, content);
            }
        }
        internal VSManager(ITextTemplatingEngineHost host, StringBuilder template) : base(host, template) 
        {
            var hostServiceProvider = host as IServiceProvider;
            if (hostServiceProvider == null)
            {
                throw new ArgumentNullException("Could not obtain IServiceProvider");
            }
            this.dte = (EnvDTE.DTE) hostServiceProvider.GetService(typeof(EnvDTE.DTE));
            if (this.dte == null)
            {
                throw new ArgumentNullException("Could not obtain DTE from host");
            }
        }
        private void ProjectSync(IEnumerable<string> keepFileNames) {
            var projectFiles = new Dictionary<string, EnvDTE.ProjectItem>();
            foreach (string keepFileName in keepFileNames)
            {
                var item = this.dte.Solution.FindProjectItem(keepFileName);
                if (item != null)
                {
                    projectFiles.Add(keepFileName, item);
                }
            }
            // Remove unused items from the project 
            /* foreach(var pair in projectFiles) // NEW
            {
                if (keepFileNames.Contains(pair.Key))
                {
                    pair.Value.Delete();
                }
            } */
            // Add missing files to the project
            foreach(string fileName in keepFileNames)
            {
                if (!projectFiles.ContainsKey(fileName))
                {       
                    EnvDTE.Project targetProj = null;
                    foreach (EnvDTE.Project proj in this.dte.Solution.Projects)
                    {
                        if (string.IsNullOrEmpty(proj.FullName))
                        {
                            continue;
                        }
                        if (fileName.Contains(Path.GetDirectoryName(proj.FullName) + @""))
                        {
                            targetProj = proj;
                            break;
                        }
                    }       
                    var targetDir = NavigateTo(targetProj, fileName);       
                    if (targetDir == null)
                    {
                        targetProj.ProjectItems.AddFromFile(fileName);
                        continue;
                    }
                    targetDir.ProjectItems.AddFromFile(fileName);
                }
            }
        }
        private void CheckoutFileIfRequired(String fileName) 
        {
            var sc = dte.SourceControl;
            if (sc != null && sc.IsItemUnderSCC(fileName) && !sc.IsItemCheckedOut(fileName))
            {
                dte.SourceControl.CheckOutItem(fileName);
            }
        }
        public EnvDTE.ProjectItem NavigateTo(EnvDTE.Project project, string path)
        {
            if (string.IsNullOrEmpty(project.FullName))
            {
                return null;
            }
            var projBase = Path.GetDirectoryName(project.FullName);
            var fileBase = Path.GetDirectoryName(path);
            var naviBase = fileBase.Replace(projBase + @"", "");
            if (string.IsNullOrEmpty(fileBase.Replace(projBase, "")))
            {
                return null;
            }
            var naviPoints = naviBase.Split('\');
            EnvDTE.ProjectItem item = null;
            EnvDTE.ProjectItems items = project.ProjectItems;
            foreach (var folder in naviPoints)
            {
                item = items.Item(folder);
                items = item.ProjectItems;
            }
            return item;
        }
    }
} #>

Answer 3

在没有插件的情况下，我发现最简单的方法是右键单击目标项目，然后转到Add->Existing Item并选择生成的文件。这将在项目的根目录下为您创建一个文件副本，然后您可以根据需要移动该副本。这使您可以轻松地将生成的文件传输到除生成文件之外的项目中。

我还没有测试过当.tt文件本身位于项目的根目录中时会发生什么，但只要.tt位于子文件夹中，这肯定是有效的（无论如何，这可能是一种很好的做法）。