将T4模板输出复制到新文件中

Question

我正在尝试使用T4模板来使我们系统的迁移生成变得更加容易。但有一件事情我还不能完全弄清楚（这让我开始怀疑我是否在错误地使用T4模板），就是如何将渲染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文件的内容，但这与我的整个“让事情变得更容易”的理念有些不符。

以下是我的模板。渲染后，它应该被复制到同一目录下的“62-CreateWidgetsTable.cs”中。目标是获得一个文件，现在我可以编辑它（换句话说，我正在生成一个模板，而不是生成完整的文件）。如果我能在VS中重命名生成的文件（然后让t4生成一个新模板，直到有人来使用它），那就足够好了。

  <#@ 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()
      {

      }
    }
  }

- davidtbernal

---

我的回答没有解决你的问题吗？ - benwasd

Ben！我会尽快试一下的。这周我非常忙，所以还没有看过这个。不过我会的！ - davidtbernal

嘿，抱歉Ben，我找到了一个比你建议的方法简单得多的方式来做这个。不过还是谢谢你的帮助！ - davidtbernal

Answer 1

好的，我找到了几种做法。最简单的方法（在我展示即将介绍的方法之后才找到）在这里：t4 append output to existing file。关键信息是GenerationEnvironment是一个StringBuilder，其中包含运行模板的结果，因此您可以将该结果直接写入任何文件中！

另一种方法是使用T4 Toolbox。去下载吧！

然后，您可以创建一个模板，创建一个扩展Template的类（由T4工具箱定义），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();
    }
}
#>

- davidtbernal

Answer 2

在一些项目中，我已经使用了下面的FileManager类。它是基于这篇博客文章的自定义实现：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;
        }
    }
} #>

- benwasd

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，然后选择添加 -> 现有项目并选择您生成的文件。这会在项目的根目录下为您复制该文件，然后您可以根据需要移动它。这使您可以轻松地将生成的文件传输到除生成它们的项目之外的其他项目中。

我还没有测试过 .tt 文件本身在项目根目录中会发生什么，但只要 .tt 在子文件夹中（这可能是个好习惯），这肯定有效。

- ketura