MVC ---- Manager.ttinclude内容

http://www.infoq.com/cn/news/2009/11/T4-Multiple-Output

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，使用例子：

<#@ 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); #>