【转】- 使用T4模板批量生成代码

前言

之前在 “使用T4模板生成代码 - 初探” 文章简单的使用了T4模板的生成功能，但对于一个模板生成多个实例文件，如何实现这个方式呢？无意发现一个解决方案 “MultipleOutputHelper.ttinclude” ，它让基于T4模板批量生成文件实例变得简单起来了。

什么是MultipleOutputHelper.ttinclude

Damien Guard是一个在加利福尼亚州圣何塞的开发人员，他构建出处理使用T4模板输出多文件的解决方案“MultipleOutputHelper.ttinclude”

使用

1. 初始化

获取MultipleOutputHelper.ttinclude文件模板

注意： 文件可以上github.com 托管上面获取（https://github.com/damieng/DamienGKit/tree/master/T4/MultipleOutputHelper）

在T4模板中使用include指令导入MultipleOutputHelper.ttinclude文件或者将MultipleOutputHelper.ttinclude的代码复制在T4模板内。

然后初始化Manager对象,代码如下：

 注意： 这里的Manager.ttinclude 就是MultipleOutputHelper.ttinclude文件模板

2. 文件块

使用代码标识区分生成的代码块的范围

该代码声明了一个Employee.generated.cs文件，文件代码内容为：

1	public class Employee { ... }

3. 页眉和页脚

很多模板需要共享一个共同的页眉和页脚时，可以使用import语句进行打开和关闭。简单的使用StartHeader和StartFooter的代码方法进行分割。

4. 编译执行

使用Process方法，进行文件分割。

场景应用

基于之前的“使用T4模板生成代码 - 初探” 文章的场景，进行基于NHibernate Mapper 来获取Domain对象，然后进行批量生成多个代码文件。

1. 自定义T4模板，文件名为“EntityRepositoryTemplate.tt”，代码如下：

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<#@ template  language="C#"    debug="true" hostspecific="True"#> //  导入MultipleOutputHelper.ttinclude文件 <#@include file="$(SolutionDir)app\T4\MultipleOutputHelper.ttinclude"#> // 导入相关的DLL <#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\NHibernate.dll" #> <#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\SharpArch.NHibernate.dll" #> <#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\SharpArch.Domain.dll" #> <#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\FluentNHibernate.dll" #> <#@ Assembly Name="$(SolutionDir)app\Cotide.Data\bin\$(ConfigurationName)\Cotide.Infrastructure.dll" #> <#@ Assembly Name="$(SolutionDir)app\Cotide.Core\bin\$(ConfigurationName)\Cotide.Domain.dll" #> <#@ Assembly Name="$(SolutionDir)app\Cotide.Framework\bin\$(ConfigurationName)\Cotide.Framework.dll" #> <#@ import namespace="System.IO"#> <#@ import namespace="System"#> <#@ import namespace="System.Configuration"#>    <#      // 初始化     SharpArch.NHibernate.NHibernateSession.CloseAllSessions();     SharpArch.NHibernate.NHibernateSession.Reset();     string projectPath = @"C:\资料\Person\项目\Codeplex\电子商务\app\";     string nhibernatePath = projectPath + @"Cotide.Web\NHibernate.config";     string[] mappingAssemblies = new[] { @"C:\资料\Person\项目\Codeplex\电子商务\app\Cotide.Data\bin\Release\Cotide.Infrastructure.dll" };     // 加载配置     NHibernate.Cfg.Configuration configuration = SharpArch.NHibernate.NHibernateSession.Init(     new SharpArch.NHibernate.SimpleSessionStorage(), mappingAssemblies,     new Cotide.Infrastructure.NHibernateMaps.AutoPersistenceModelGenerator().Generate(),     nhibernatePath);     // 获取所有类映射     var allClassMetadata = SharpArch.NHibernate.NHibernateSession.GetDefaultSessionFactory().GetAllClassMetadata();     var manager = Manager.Create(Host, GenerationEnvironment);      foreach (var entry in allClassMetadata)     {        var entityName = entry.Value.EntityName.Split('.');        var className = entityName[entityName.Length - 1];         // 定义输出文件         manager.StartNewFile("I"+className+"Repository.cs");        #>//------------------------------------------------------------------- //版权所有：版权所有(C) 2012，Microsoft(China) Co.,LTD //系统名称： //文件名称：I<#=className#>Repository.cs //模块名称： //模块编号： //作　　者：xcli //创建时间：2013/4/6 12:49:50 //功能说明： //----------------------------------------------------------------- //修改记录： //修改人：   //修改时间： //修改内容： //-----------------------------------------------------------------  using System; using System.Collections.Generic; using System.Linq; using System.Text; using Cotide.Domain.Contracts.Repositories.Extension; namespace Cotide.Domain.Contracts.Repositories {         public interface I<#=className#>Repository : IDbProxyRepository<<#=className#>>         {           } }    <#        // 结束输出文件        manager.EndBlock();     }        // 执行编译        manager.Process(true);      #>

输出文件效果：

让程序自动执行基于T4文件的编译工作

在MSDN-”演练：创建自定义文本模板宿主“ 文章里面看到一段代码，进行了T4文件的编译工作,代码如下：

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using System; using System.IO; using System.CodeDom.Compiler; using System.Collections.Generic; using System.Text; using Microsoft.VisualStudio.TextTemplating;   namespace CustomHost {     //The text template transformation engine is responsible for running     //the transformation process.     //The host is responsible for all input and output, locating files,     //and anything else related to the external environment.     //-------------------------------------------------------------------------     class CustomCmdLineHost : ITextTemplatingEngineHost     {         //the path and file name of the text template that is being processed         //---------------------------------------------------------------------         internal string TemplateFileValue;         public string TemplateFile         {             get { return TemplateFileValue; }         }         //This will be the extension of the generated text output file.         //The host can provide a default by setting the value of the field here.         //The engine can change this value based on the optional output directive         //if the user specifies it in the text template.         //---------------------------------------------------------------------         private string fileExtensionValue = ".txt";         public string FileExtension         {             get { return fileExtensionValue; }         }         //This will be the encoding of the generated text output file.         //The host can provide a default by setting the value of the field here.         //The engine can change this value based on the optional output directive         //if the user specifies it in the text template.         //---------------------------------------------------------------------         private Encoding fileEncodingValue = Encoding.UTF8;         public Encoding FileEncoding         {             get { return fileEncodingValue; }         }         //These are the errors that occur when the engine processes a template.         //The engine passes the errors to the host when it is done processing,         //and the host can decide how to display them. For example, the host         //can display the errors in the UI or write them to a file.         //---------------------------------------------------------------------         private CompilerErrorCollection errorsValue;         public CompilerErrorCollection Errors         {             get { return errorsValue; }         }         //The host can provide standard assembly references.         //The engine will use these references when compiling and         //executing the generated transformation class.         //--------------------------------------------------------------         public IList<string> StandardAssemblyReferences         {             get             {                 return new string[]                 {                     //If this host searches standard paths and the GAC,                     //we can specify the assembly name like this.                     //---------------------------------------------------------                     //"System"                       //Because this host only resolves assemblies from the                     //fully qualified path and name of the assembly,                     //this is a quick way to get the code to give us the                     //fully qualified path and name of the System assembly.                     //---------------------------------------------------------                     typeof(System.Uri).Assembly.Location                 };             }         }         //The host can provide standard imports or using statements.         //The engine will add these statements to the generated         //transformation class.         //--------------------------------------------------------------         public IList<string> StandardImports         {             get             {                 return new string[]                 {                     "System"                 };             }         }         //The engine calls this method based on the optional include directive         //if the user has specified it in the text template.         //This method can be called 0, 1, or more times.         //---------------------------------------------------------------------         //The included text is returned in the context parameter.         //If the host searches the registry for the location of include files,         //or if the host searches multiple locations by default, the host can         //return the final path of the include file in the location parameter.         //---------------------------------------------------------------------         public bool LoadIncludeText(string requestFileName, out string content, out string location)         {             content = System.String.Empty;             location = System.String.Empty;                      //If the argument is the fully qualified path of an existing file,             //then we are done.             //----------------------------------------------------------------             if (File.Exists(requestFileName))             {                 content = File.ReadAllText(requestFileName);                 return true;             }             //This can be customized to search specific paths for the file.             //This can be customized to accept paths to search as command line             //arguments.             //----------------------------------------------------------------             else             {                 return false;             }         }         //Called by the Engine to enquire about         //the processing options you require.         //If you recognize that option, return an         //appropriate value.         //Otherwise, pass back NULL.         //--------------------------------------------------------------------         public object GetHostOption(string optionName)         {         object returnObject;         switch (optionName)         {         case "CacheAssemblies":                     returnObject = true;      break;         default:         returnObject = null;         break;         }         return returnObject;         }         //The engine calls this method to resolve assembly references used in         //the generated transformation class project and for the optional         //assembly directive if the user has specified it in the text template.         //This method can be called 0, 1, or more times.         //---------------------------------------------------------------------         public string ResolveAssemblyReference(string assemblyReference)         {             //If the argument is the fully qualified path of an existing file,             //then we are done. (This does not do any work.)             //----------------------------------------------------------------             if (File.Exists(assemblyReference))             {                 return assemblyReference;             }             //Maybe the assembly is in the same folder as the text template that             //called the directive.             //----------------------------------------------------------------             string candidate = Path.Combine(Path.GetDirectoryName(this.TemplateFile), assemblyReference);             if (File.Exists(candidate))             {                 return candidate;             }             //This can be customized to search specific paths for the file             //or to search the GAC.             //----------------------------------------------------------------             //This can be customized to accept paths to search as command line             //arguments.             //----------------------------------------------------------------             //If we cannot do better, return the original file name.             return "";         }         //The engine calls this method based on the directives the user has         //specified in the text template.         //This method can be called 0, 1, or more times.         //---------------------------------------------------------------------         public Type ResolveDirectiveProcessor(string processorName)         {             //This host will not resolve any specific processors.             //Check the processor name, and if it is the name of a processor the             //host wants to support, return the type of the processor.             //---------------------------------------------------------------------             if (string.Compare(processorName, "XYZ", StringComparison.OrdinalIgnoreCase) == 0)             {                 //return typeof();             }             //This can be customized to search specific paths for the file             //or to search the GAC             //If the directive processor cannot be found, throw an error.             throw new Exception("Directive Processor not found");         }         //A directive processor can call this method if a file name does not         //have a path.         //The host can attempt to provide path information by searching         //specific paths for the file and returning the file and path if found.         //This method can be called 0, 1, or more times.         //---------------------------------------------------------------------         public string ResolvePath(string fileName)         {             if (fileName == null)             {                 throw new ArgumentNullException("the file name cannot be null");             }             //If the argument is the fully qualified path of an existing file,             //then we are done             //----------------------------------------------------------------             if (File.Exists(fileName))             {                 return fileName;             }             //Maybe the file is in the same folder as the text template that             //called the directive.             //----------------------------------------------------------------             string candidate = Path.Combine(Path.GetDirectoryName(this.TemplateFile), fileName);             if (File.Exists(candidate))             {                 return candidate;             }             //Look more places.             //----------------------------------------------------------------             //More code can go here...             //If we cannot do better, return the original file name.             return fileName;         }         //If a call to a directive in a text template does not provide a value         //for a required parameter, the directive processor can try to get it         //from the host by calling this method.         //This method can be called 0, 1, or more times.         //---------------------------------------------------------------------         public string ResolveParameterValue(string directiveId, string processorName, string parameterName)         {             if (directiveId == null)             {                 throw new ArgumentNullException("the directiveId cannot be null");             }             if (processorName == null)             {                 throw new ArgumentNullException("the processorName cannot be null");             }             if (parameterName == null)             {                 throw new ArgumentNullException("the parameterName cannot be null");             }             //Code to provide "hard-coded" parameter values goes here.             //This code depends on the directive processors this host will interact with.             //If we cannot do better, return the empty string.             return String.Empty;         }         //The engine calls this method to change the extension of the         //generated text output file based on the optional output directive         //if the user specifies it in the text template.         //---------------------------------------------------------------------         public void SetFileExtension(string extension)         {             //The parameter extension has a '.' in front of it already.             //--------------------------------------------------------             fileExtensionValue = extension;         }         //The engine calls this method to change the encoding of the         //generated text output file based on the optional output directive         //if the user specifies it in the text template.         //----------------------------------------------------------------------         public void SetOutputEncoding(System.Text.Encoding encoding, bool fromOutputDirective)         {             fileEncodingValue = encoding;         }         //The engine calls this method when it is done processing a text         //template to pass any errors that occurred to the host.         //The host can decide how to display them.         //---------------------------------------------------------------------         public void LogErrors(CompilerErrorCollection errors)         {             errorsValue = errors;         }         //This is the application domain that is used to compile and run         //the generated transformation class to create the generated text output.         //----------------------------------------------------------------------         public AppDomain ProvideTemplatingAppDomain(string content)         {             //This host will provide a new application domain each time the             //engine processes a text template.             //-------------------------------------------------------------             return AppDomain.CreateDomain("Generation App Domain");             //This could be changed to return the current appdomain, but new             //assemblies are loaded into this AppDomain on a regular basis.             //If the AppDomain lasts too long, it will grow indefintely,             //which might be regarded as a leak.             //This could be customized to cache the application domain for             //a certain number of text template generations (for example, 10).             //This could be customized based on the contents of the text             //template, which are provided as a parameter for that purpose.         }     }     //This will accept the path of a text template as an argument.     //It will create an instance of the custom host and an instance of the     //text templating transformation engine, and will transform the     //template to create the generated text output file.     //-------------------------------------------------------------------------     class Program     {         static void Main(string[] args)         {             try             {                 ProcessTemplate(args);             }             catch (Exception ex)             {                 Console.WriteLine(ex.Message);             }         }         static void ProcessTemplate(string[] args)         {             string templateFileName = null;             if (args.Length == 0)             {                 throw new System.Exception("you must provide a text template file path");             }             templateFileName = args[0];             if (templateFileName == null)             {                 throw new ArgumentNullException("the file name cannot be null");             }             if (!File.Exists(templateFileName))             {                 throw new FileNotFoundException("the file cannot be found");             }             CustomCmdLineHost host = new CustomCmdLineHost();             Engine engine = new Engine();             host.TemplateFileValue = templateFileName;             //Read the text template.             string input = File.ReadAllText(templateFileName);             //Transform the text template.             string output = engine.ProcessTemplate(input, host);             string outputFileName = Path.GetFileNameWithoutExtension(templateFileName);             outputFileName = Path.Combine(Path.GetDirectoryName(templateFileName), outputFileName);             outputFileName = outputFileName + "1" + host.FileExtension;             File.WriteAllText(outputFileName, output, host.FileEncoding);               foreach (CompilerError error in host.Errors)             {                 Console.WriteLine(error.ToString());             }         }     } }

联想：基于这个代码实例，可以做一个基于T4模板来批量输出代码的小工具,待续.....

参考资料

• MultipleOutputHelper.ttinclude 文件作者（Damien Guard）- 博客（ http://damieng.com ）
• Damien Guard （Github）（ https://github.com/damieng）
• 创建自定义文本模板宿主( ＭＳＤＮ) ( http://msdn.microsoft.com/zh-cn/library/vstudio/bb126579.aspx )
• 使用T4模板生成代码 - 初探 （ http://www.cotide.com/xcli/Blog/Article/44 ）

转自 http://www.cnblogs.com/K_tommy/archive/2013/04/06/T4.html