T4语法快速入门

1.什么是T4?

 T4，即4个T开头的英文字母组合：Text Template Transformation Toolkit。T4(Text Template Transformation Toolkit)是微软官方在VisualStudio 2008中开始使用的代码生成引擎。简单的说就是可以根据模板生成你想要的文件，可以使类文件,文本文件,HTML等等。

2.vs插件的安装

T4的编辑工具下载地址http://t4-editor.tangible-engineering.com/Download_T4Editor_Plus_ModelingTools.html
VS默认的编辑工具无高亮，无提示，错误不易定位。 没这个工具，真心不想写任何T4代码。

 3.T4语法

<# 标准控制块 #> 可以包含语句。

<#= 表达式控制块 #> 可以包含表达式。

<#+ 类特征控制块 #> 可以包含方法、字段和属性，就像一个类的内部

<#@ 指令 属性=“值”#>

3.1.标准控制块

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ import namespace="System" #>
<#@ output extension=".txt" #>

<#
    int a=10;
    string b = "20"; 
    DateTime c = DateTime.Now;
    for(int i = 0; i < 4; i++)
    {
#>
测试
<#
    } 
    
#>

3.2.表达式控制块

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ import namespace="System" #>
<#@ output extension=".txt" #>

<#
    int a=10;
    string b = "20"; 
    DateTime c = DateTime.Now;
    for(int i = 0; i < 4; i++)
    {
#>
测试<#=i#> <#=string.Format("{0},{1},{2}",a,b,c)#>
<#
    } 
    
#>

3.3.类特征控制块

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ import namespace="System" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ output extension=".txt" #>



<#
    int a=10;
    string b = "20"; 
    DateTime c = DateTime.Now;
    for(int i = 0; i < 4; i++)
    {
#>
测试<#=i#> 
<#=string.Format("{0},{1},{2}",a,b,c)#>
<#=1+1#>
<#=config.TableName#>
<#
    } 
    
#>
<#+
    public class config
    {
        public static readonly string ConnectionString = "Data Source=(local);Initial Catalog=NFineBase;User ID=sa;Password=hjf19870810;";
        public static readonly string DbDatabase = "NFineBase";
        public static readonly string TableName = "Sys_Test";
    }
#>

3.4.指令

<#@ output extension=".cs" #>
告诉T4引擎生成文件的后缀名是.cs；

<#@ template debug="false" hostspecific="false" language="C#" #>
langeuage:输出语言，有效值C#、VB，默认为C#
debug:是否启用调试，有效值true、false，默认为false。
hostspecific:有效值true、false，默认为false。如果将此特性的值设置为 true，则会将名为 Host 的属性添加到由文本模板生成的类中。 该属性是对转换引擎的宿主的引用，并声明为Microsoft.VisualStudio.TextTemplating.ITextTemplatingEngineHost。
inherits：可以指定模板的程序代码可以继承自另一个类，这个类也可以从文本模板生成。目前木有使用过，基本上可以忽略

<#@ assembly name="System"#>
告诉T4引擎编译运行时引用System程序集

<#@ import namespace="System.Data"#>
告诉T4引擎编译运行时引用某个名称空间。

 3.5.实战

<#+
    public class DbHelper
    {
        public static readonly string connectionString="Data Source=GZPC0114;User ID=sa;Password=abc.123;persist security info=False;initial catalog=suibao_jz_db;";
        //public static readonly string connectionString="Data Source=192.168.10.135;User ID=sa;Password=111111;persist security info=False;initial catalog=suibao_jz_db;";
        public static readonly string database="suibao_jz_db";

        #region GetDbTables
        
        public static List<DbTable> GetDbTables()
        {
            string tables = null;
            if (!string.IsNullOrEmpty(tables))
            {
                tables = string.Format(" and obj.name in ('{0}')", tables.Replace(",", "','"));
            }
            #region SQL
            string sql = string.Format(@"SELECT
                                    obj.name tablename,
                                    schem.name schemname,
                                    CAST
                                    (
                                        CASE 
                                            WHEN (SELECT COUNT(1) FROM sys.indexes WHERE object_id= obj.OBJECT_ID AND is_primary_key=1) >=1 THEN 1
                                            ELSE 0
                                        END 
                                    AS BIT) HasPrimaryKey                                         
                                    from {0}.sys.objects obj 
                                    INNER JOIN {0}.sys.schemas schem ON obj.schema_id=schem.schema_id
                                    where type='U' or type='V' {1}
                                    order by obj.name", database, tables);
            #endregion
            DataTable dt = GetDataTable(sql);
            return dt.Rows.Cast<DataRow>().Select(row => new DbTable
            {
                TableName = row.Field<string>("tablename"),
                SchemaName = row.Field<string>("schemname"),
                HasPrimaryKey = row.Field<bool>("HasPrimaryKey")
            }).ToList();
        }
        #endregion

        #region GetDbColumns
        
        public static List<DbColumn> GetDbColumns(string tableName, string schema = "dbo")
        {
            #region SQL
            string sql = string.Format(@"
                                    WITH indexCTE AS
                                    (
                                        SELECT 
                                        ic.column_id,
                                        ic.index_column_id,
                                        ic.object_id    
                                        FROM {0}.sys.indexes idx
                                        INNER JOIN {0}.sys.index_columns ic ON idx.index_id = ic.index_id AND idx.object_id = ic.object_id
                                        WHERE  idx.object_id =OBJECT_ID(@tableName) AND idx.is_primary_key=1
                                    )
                                    select
                                    colm.column_id ColumnID,
                                    CAST(CASE WHEN indexCTE.column_id IS NULL THEN 0 ELSE 1 END AS BIT) IsPrimaryKey,
                                    colm.name ColumnName,
                                    systype.name ColumnType,
                                    colm.is_identity IsIdentity,
                                    colm.is_nullable IsNullable,
                                    cast(colm.max_length as int) ByteLength,
                                    (
                                        case 
                                            when systype.name='nvarchar' and colm.max_length>0 then colm.max_length/2 
                                            when systype.name='nchar' and colm.max_length>0 then colm.max_length/2
                                            when systype.name='ntext' and colm.max_length>0 then colm.max_length/2 
                                            else colm.max_length
                                        end
                                    ) CharLength,
                                    cast(colm.precision as int) Precision,
                                    cast(colm.scale as int) Scale,
                                    prop.value Remark
                                    from {0}.sys.columns colm
                                    inner join {0}.sys.types systype on colm.system_type_id=systype.system_type_id and colm.user_type_id=systype.user_type_id
                                    left join {0}.sys.extended_properties prop on colm.object_id=prop.major_id and colm.column_id=prop.minor_id
                                    LEFT JOIN indexCTE ON colm.column_id=indexCTE.column_id AND colm.object_id=indexCTE.object_id                                        
                                    where colm.object_id=OBJECT_ID(@tableName)
                                    order by colm.column_id", database);
            #endregion
            SqlParameter param = new SqlParameter("@tableName", SqlDbType.NVarChar, 100) { Value = string.Format("{0}.{1}.{2}", database, schema, tableName) };
            DataTable dt = GetDataTable(sql, param);
            return dt.Rows.Cast<DataRow>().Select(row => new DbColumn()
            {
                ColumnID = row.Field<int>("ColumnID"),
                IsPrimaryKey = row.Field<bool>("IsPrimaryKey"),
                ColumnName = row.Field<string>("ColumnName"),
                ColumnType = row.Field<string>("ColumnType"),
                IsIdentity = row.Field<bool>("IsIdentity"),
                IsNullable = row.Field<bool>("IsNullable"),
                ByteLength = row.Field<int>("ByteLength"),
                CharLength = row.Field<int>("CharLength"),
                Scale = row.Field<int>("Scale"),
                Remark = row["Remark"].ToString()
            }).ToList();
        }

        #endregion     


        #region GetDataTable
        
        public static DataTable GetDataTable(string commandText, params SqlParameter[] parms)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                SqlCommand command = connection.CreateCommand();
                command.CommandText = commandText;
                command.Parameters.AddRange(parms);
                SqlDataAdapter adapter = new SqlDataAdapter(command);

                DataTable dt = new DataTable();
                adapter.Fill(dt);

                return dt;
            }
        }

        #endregion
    }

    #region DbTable
    /// <summary>
    /// 表结构
    /// </summary>
    public sealed class DbTable
    {
        /// <summary>
        /// 表名称
        /// </summary>
        public string TableName { get; set; }
        /// <summary>
        /// 表的架构
        /// </summary>
        public string SchemaName { get; set; }
        /// <summary>
        /// 表的记录数
        /// </summary>
        public int Rows { get; set; }

        /// <summary>
        /// 是否含有主键
        /// </summary>
        public bool HasPrimaryKey { get; set; }
    }
    #endregion

    #region DbColumn
    /// <summary>
    /// 表字段结构
    /// </summary>
    public sealed class DbColumn
    {
        /// <summary>
        /// 字段ID
        /// </summary>
        public int ColumnID { get; set; }

        /// <summary>
        /// 是否主键
        /// </summary>
        public bool IsPrimaryKey { get; set; }

        /// <summary>
        /// 字段名称
        /// </summary>
        public string ColumnName { get; set; }

        /// <summary>
        /// 字段类型
        /// </summary>
        public string ColumnType { get; set; }

        /// <summary>
        /// 数据库类型对应的C#类型
        /// </summary>
        public string CSharpType
        {
            get
            {
                return SqlServerDbTypeMap.MapCsharpType(ColumnType);
            }
        }

        /// <summary>
        /// 
        /// </summary>
        public Type CommonType
        {
            get
            {
                return SqlServerDbTypeMap.MapCommonType(ColumnType);
            }
        }

        /// <summary>
        /// 字节长度
        /// </summary>
        public int ByteLength { get; set; }

        /// <summary>
        /// 字符长度
        /// </summary>
        public int CharLength { get; set; }

        /// <summary>
        /// 小数位
        /// </summary>
        public int Scale { get; set; }

        /// <summary>
        /// 是否自增列
        /// </summary>
        public bool IsIdentity { get; set; }

        /// <summary>
        /// 是否允许空
        /// </summary>
        public bool IsNullable { get; set; }

        /// <summary>
        /// 描述
        /// </summary>
        public string Remark { get; set; }
    }
    #endregion

    #region SqlServerDbTypeMap

    public class SqlServerDbTypeMap
    {
        public static string MapCsharpType(string dbtype)
        {
            if (string.IsNullOrEmpty(dbtype)) return dbtype;
            dbtype = dbtype.ToLower();
            string csharpType = "object";
            switch (dbtype)
            {
                case "bigint": csharpType = "long"; break;
                case "binary": csharpType = "byte[]"; break;
                case "bit": csharpType = "bool"; break;
                case "char": csharpType = "string"; break;
                case "date": csharpType = "DateTime"; break;
                case "datetime": csharpType = "DateTime"; break;
                case "datetime2": csharpType = "DateTime"; break;
                case "datetimeoffset": csharpType = "DateTimeOffset"; break;
                case "decimal": csharpType = "decimal"; break;
                case "float": csharpType = "double"; break;
                case "image": csharpType = "byte[]"; break;
                case "int": csharpType = "int"; break;
                case "money": csharpType = "decimal"; break;
                case "nchar": csharpType = "string"; break;
                case "ntext": csharpType = "string"; break;
                case "numeric": csharpType = "decimal"; break;
                case "nvarchar": csharpType = "string"; break;
                case "real": csharpType = "Single"; break;
                case "smalldatetime": csharpType = "DateTime"; break;
                case "smallint": csharpType = "short"; break;
                case "smallmoney": csharpType = "decimal"; break;
                case "sql_variant": csharpType = "object"; break;
                case "sysname": csharpType = "object"; break;
                case "text": csharpType = "string"; break;
                case "time": csharpType = "TimeSpan"; break;
                case "timestamp": csharpType = "byte[]"; break;
                case "tinyint": csharpType = "byte"; break;
                case "uniqueidentifier": csharpType = "Guid"; break;
                case "varbinary": csharpType = "byte[]"; break;
                case "varchar": csharpType = "string"; break;
                case "xml": csharpType = "string"; break;
                default: csharpType = "object"; break;
            }
            return csharpType;
        }
           
        public static Type MapCommonType(string dbtype)
        {
            if (string.IsNullOrEmpty(dbtype)) return Type.Missing.GetType();
            dbtype = dbtype.ToLower();
            Type commonType = typeof(object);
            switch (dbtype)
            {
                case "bigint": commonType = typeof(long); break;
                case "binary": commonType = typeof(byte[]); break;
                case "bit": commonType = typeof(bool); break;
                case "char": commonType = typeof(string); break;
                case "date": commonType = typeof(DateTime); break;
                case "datetime": commonType = typeof(DateTime); break;
                case "datetime2": commonType = typeof(DateTime); break;
                case "datetimeoffset": commonType = typeof(DateTimeOffset); break;
                case "decimal": commonType = typeof(decimal); break;
                case "float": commonType = typeof(double); break;
                case "image": commonType = typeof(byte[]); break;
                case "int": commonType = typeof(int); break;
                case "money": commonType = typeof(decimal); break;
                case "nchar": commonType = typeof(string); break;
                case "ntext": commonType = typeof(string); break;
                case "numeric": commonType = typeof(decimal); break;
                case "nvarchar": commonType = typeof(string); break;
                case "real": commonType = typeof(Single); break;
                case "smalldatetime": commonType = typeof(DateTime); break;
                case "smallint": commonType = typeof(short); break;
                case "smallmoney": commonType = typeof(decimal); break;
                case "sql_variant": commonType = typeof(object); break;
                case "sysname": commonType = typeof(object); break;
                case "text": commonType = typeof(string); break;
                case "time": commonType = typeof(TimeSpan); break;
                case "timestamp": commonType = typeof(byte[]); break;
                case "tinyint": commonType = typeof(byte); break;
                case "uniqueidentifier": commonType = typeof(Guid); break;
                case "varbinary": commonType = typeof(byte[]); break;
                case "varchar": commonType = typeof(string); break;
                case "xml": commonType = typeof(string); break;
                default: commonType = typeof(object); break;
            }
            return commonType;
        }
    }
    #endregion
    

#>

<#@ template language="C#" debug="false" hostspecific="true"#>
<#@ output extension=".txt" #>
<#@ assembly name="System.Core.dll" #>
<#@ assembly name="System.Data.dll" #>
<#@ assembly name="System.Data.DataSetExtensions.dll" #>
<#@ assembly name="System.Xml.dll" #>
<#@ import namespace="System" #>
<#@ import namespace="System.Xml" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Data" #>
<#@ import namespace="System.Data.SqlClient" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ import namespace="System.IO" #>
<#@ include file="DbHelper.ttinclude"  #>

<#
 var tables=DbHelper.GetDbTables();
 #> 



 <# foreach(DbTable entity in tables){#>
    表名称<#=entity.TableName#>
    字段开始----------------    
    <#    var Columns = DbHelper.GetDbColumns(entity.TableName);
        foreach(var col in Columns){#>
        字段：<#=col.ColumnName#> 类型：<#=col.ColumnType#>
    <#    
    }
    #>
字段结束----------------
 <# } #>
        

效果：

 例子2

<#@ 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));
        }
    }
} #>

<#@ template language="C#" debug="false" hostspecific="true"#>
<#@ output extension=".txt" #>

<#@ assembly name="System.Data.dll" #>
<#@ assembly name="System.Data.DataSetExtensions.dll" #>

<#@ import namespace="System" #>
<#@ import namespace="System.Xml" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Data" #>
<#@ import namespace="System.Data.SqlClient" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ import namespace="System.IO" #>
<#@ include file="DbHelper.ttinclude"  #>
<#@ include file="Manager.ttinclude"  #>
<#
    var manager= Manager.Create(Host,GenerationEnvironment);
    var tables=DbHelper.GetDbTables();
    string[] TableNameList = new string[]{"ProductSeries_Content","Tree_Content_Tree","ProductSeries_Series","ProductSeries_Series_UserDefine"};
#>

        
 <# 
    foreach(DbTable entity in tables)
    {
        if(TableNameList.Contains(entity.TableName))
        {
            manager.StartNewFile(entity.TableName+".cs");#>     
            using System;
            using System.ComponentModel.DataAnnotations.Schema;
            using System.Data.Entity.ModelConfiguration;
            namespace SuiBao.Models
{
                public class <#=entity.TableName#>Configuration : EntityTypeConfiguration<<#=entity.TableName#>>
                {
                    public <#=entity.TableName#>Configuration()
                    {
                        ToTable("<#=entity.TableName#>");
                        HasKey(x => x.<#=DbHelper.GetDbColumns(entity.TableName).SingleOrDefault(x=>x.IsPrimaryKey == true).ColumnName#>);

                    }
                }
             public class <#=entity.TableName#>
             {
               <#    var Columns = DbHelper.GetDbColumns(entity.TableName);
        foreach(var col in Columns){#>
        public <#=col.CSharpType#> <#=col.ColumnName#> {get;set;}
    <#    
    }
    #>
        public <#=entity.TableName#>()
        {
            <#foreach(var col in Columns)
            {
        if(col.CSharpType == "string"){#>
        this.<#=col.ColumnName#> = string.Empty;
        <#}else if(col.CSharpType == "int"){#>
        this.<#=col.ColumnName#> = 0;
        <#}else if(col.CSharpType == "long"){#>
        this.<#=col.ColumnName#> = 0;
        <#}else if(col.CSharpType == "DateTime"){#>
        this.<#=col.ColumnName#> = DateTime.MinValue;
        <#}else if(col.CSharpType == "Guid"){#>
        this.<#=col.ColumnName#> = Guid.Empty;
        <#}else {}#>

            <#}#>
        }
    }}
             <# manager.EndBlock();
        }
        else
            continue;
    }
    manager.Process(true);
#>