转自:http://blog.csdn.net/cracklibby/article/details/51319799
初次认识并尝试使用T4生成代码的时候,相关学习资料似乎比较少。不过现在VS2010 的MSDN里已有相关章节,可参看《代码生成和文本模板》章节。可以用C#的语法写模板,实在舒服很多。
很快就发现T4难以生成多个文件的缺陷,微软似乎也不着急改进这一点。通过搜索,从InfoQ找到一篇文章《用T4生成多个文件》,链接到一篇文章,Damien Guard的扩展可以方便的生成多个文件。原文是英文,能看懂,然而如果翻译则斟酌字词太辛苦。
首先,保存以下代码为一个模板文件(例如保存文件名为Manager.ttinclude):
<#@ 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 class Manager { private class Block { public String Name; public int Start, Length; } private Block currentBlock; private List<Block> files = new List<Block>(); private Block footer = new Block(); private Block header = new Block(); private ITextTemplatingEngineHost host; private StringBuilder template; protected List<String> generatedFileNames = new List<String>(); public static Manager Create(ITextTemplatingEngineHost host, StringBuilder template) { return (host is IServiceProvider) ? new VSManager(host, template) : new Manager(host, 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; } public virtual void Process(bool split) { if (split) { EndBlock(); String headerText = template.ToString(header.Start, header.Length); String footerText = template.ToString(footer.Start, footer.Length); String outputPath = Path.GetDirectoryName(host.TemplateFile); files.Reverse(); foreach(Block block in files) { String fileName = Path.Combine(outputPath, block.Name); String content = headerText + template.ToString(block.Start, block.Length) + footerText; generatedFileNames.Add(fileName); CreateFile(fileName, content); template.Remove(block.Start, block.Length); } } } protected virtual void CreateFile(String fileName, String content) { if (IsFileContentDifferent(fileName, content)) File.WriteAllText(fileName, content); } public virtual String GetCustomToolNamespace(String fileName) { return null; } public virtual String DefaultProjectNamespace { get { return null; } } protected bool IsFileContentDifferent(String fileName, String newContent) { return !(File.Exists(fileName) && File.ReadAllText(fileName) == newContent); } private Manager(ITextTemplatingEngineHost host, StringBuilder template) { this.host = host; this.template = template; } private Block CurrentBlock { get { return currentBlock; } set { if (CurrentBlock != null) EndBlock(); if (value != null) value.Start = template.Length; currentBlock = value; } } private class VSManager: Manager { private EnvDTE.ProjectItem templateProjectItem; private EnvDTE.DTE dte; private Action<String> checkOutAction; private Action<IEnumerable<String>> projectSyncAction; 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(bool split) { if (templateProjectItem.ProjectItems == null) return; base.Process(split); projectSyncAction.EndInvoke(projectSyncAction.BeginInvoke(generatedFileNames, null, null)); } 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 = (IServiceProvider) host; if (hostServiceProvider == null) throw new ArgumentNullException("Could not obtain IServiceProvider"); dte = (EnvDTE.DTE) hostServiceProvider.GetService(typeof(EnvDTE.DTE)); if (dte == null) throw new ArgumentNullException("Could not obtain DTE from host"); templateProjectItem = dte.Solution.FindProjectItem(host.TemplateFile); checkOutAction = (String fileName) => dte.SourceControl.CheckOutItem(fileName); projectSyncAction = (IEnumerable<String> keepFileNames) => ProjectSync(templateProjectItem, keepFileNames); } private static void ProjectSync(EnvDTE.ProjectItem templateProjectItem, IEnumerable<String> keepFileNames) { var keepFileNameSet = new HashSet<String>(keepFileNames); var projectFiles = new Dictionary<String, EnvDTE.ProjectItem>(); var originalFilePrefix = Path.GetFileNameWithoutExtension(templateProjectItem.get_FileNames(0)) + "."; foreach(EnvDTE.ProjectItem projectItem in templateProjectItem.ProjectItems) projectFiles.Add(projectItem.get_FileNames(0), projectItem); // Remove unused items from the project foreach(var pair in projectFiles) if (!keepFileNames.Contains(pair.Key) && !(Path.GetFileNameWithoutExtension(pair.Key) + ".").StartsWith(originalFilePrefix)) pair.Value.Delete(); // Add missing files to the project foreach(String fileName in keepFileNameSet) if (!projectFiles.ContainsKey(fileName)) templateProjectItem.ProjectItems.AddFromFile(fileName); } private void CheckoutFileIfRequired(String fileName) { var sc = dte.SourceControl; if (sc != null && sc.IsItemUnderSCC(fileName) && !sc.IsItemCheckedOut(fileName)) checkOutAction.EndInvoke(checkOutAction.BeginInvoke(fileName, null, null)); } } } #>
接着,在T4模板文件里引用这个模板,并声明一个Manager类实例:
<#@ template language="C#" hostspecific="True"#> <#@include file="Manager.ttinclude"#> <# var manager = Manager.Create(Host, GenerationEnvironment); #>
使用两行代码可使代码输出到单独文件,你要输出的代码可写在这两个语句中间,StartNewFile的参数就是输出的文件名:
<# manager.StartNewFile("Employee.generated.cs"); #> <# manager.EndBlock(); #>
比如可以这样写:
<# manager.StartNewFile("Employee.generated.cs"); #> public class Employee { } <# manager.EndBlock(); #>
还可以为每个输出文件输出同样的头部或顶部,只需要相应的语句:
<# manager.StartHeader(); #> // Code generated by a template using System; <# manager.EndBlock(); #> <# manager.StartFooter(); #> // It's the end <# manager.EndBlock(); #>
最后使用这句来执行输出多个文件:
<# manager.Process(true); #>