T4模版

T4模版

这讲适合所有的MVC程序

很荣幸，我们的系统有了体验的地址了。演示地址

之前我们发布了一个简单的代码生成器，其原理就是读取数据库的表结构，生成文本的一个方式来生成代码！

为了替代重复的劳动，微软自己有一套T4模版，我不想把T4模版说得那么的复杂，因为这个复杂我自己也不知道。

原理跟市面的代码生成器一个道理，但是T4的扩展比代码生成器更灵活，可以更方便根据类生成代码等操作。

T4代码模式是没有颜色高亮了，但是我们的VS支持插件 T4 Editor

下载安装之后就可以跟我们写C#一样有智能高亮和提示了。

新建一个项目，专门用于T4的存放。

首先我们要让T4连接我们的数据库

新建一个DbHelper.ttinclude模版包含文件

 DbHelper.ttinclude
<#+
    public class DbHelper
    {
        #region GetDbTables

        public static List<DbTable> GetDbTables(string connectionString, string database, 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,
                                    idx.rows,
                                    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}.dbo.sysindexes idx on obj.object_id=idx.id and idx.indid<=1
                                    INNER JOIN {0}.sys.schemas schem ON obj.schema_id=schem.schema_id
                                    where type='U' {1}
                                    order by obj.name", database, tables);
            #endregion
            DataTable dt = GetDataTable(connectionString, sql);
            return dt.Rows.Cast<DataRow>().Select(row => new DbTable
            {
                TableName = row.Field<string>("tablename"),
                SchemaName = row.Field<string>("schemname"),
                Rows = row.Field<int>("rows"),
                HasPrimaryKey = row.Field<bool>("HasPrimaryKey")
            }).ToList();
        }
        #endregion
        #region GetDbColumns

        public static List<DbColumn> GetDbColumns(string connectionString, string database, 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(connectionString, 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 connectionString, 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

#>
DbHelper.ttinclude

这里面包含了一些转换的方法和访问数据库的SQL语句

其中GetDbTables方法就是根据数据库的链接，表名来读取字段数据

怎么用呢？就是让模版包含这个文件，就可以访问方法了

举一个Model为例吧，新建Model文件夹。并新建文件，模版文件为tt结尾的扩展

我们新建Test.tt之后

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

最后一行<#@ output extension=".txt" #>

为模版生成的文件，可以是.cs可以是其他。我们就不改了，就是txt

如果是cs类，生成会编译，如果代码是对的，但是系统不知道是对的，会编译出错，虽然这不影响结果，但是不爽

我们为Test.tt添加如下代码

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ 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="$(ProjectDir)DbHelper.ttinclude"  #>
//------------------------------------------------------------------------------
// <auto-generated>
//     此代码由T4模板自动生成
//       生成时间 <#=DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")#> by YmNets
//     对此文件的更改可能会导致不正确的行为，并且如果
//     重新生成代码，这些更改将会丢失。
// </auto-generated>
//------------------------------------------------------------------------------

我们引入了一些命名空间，因为我们要将读到的表结构进行一系列的处理，比如for循环等操作

其中<#@ include file="$(ProjectDir)DbHelper.ttinclude"  #>就是包含了刚刚简历的访问数据库文件

T4模版的语法通过上面我们可以看出是<#@#>,<#=#>,<##>,<#+#>结构跟原生的asp.net一个鸟样，不是Razor语法，这里要注意

我们添加一些代码

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ 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="$(ProjectDir)DbHelper.ttinclude"  #>
//------------------------------------------------------------------------------
// <auto-generated>
//     此代码由T4模板自动生成
//       生成时间 <#=DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")#> by YmNets
//     对此文件的更改可能会导致不正确的行为，并且如果
//     重新生成代码，这些更改将会丢失。
// </auto-generated>
//------------------------------------------------------------------------------
using System;
using System.ComponentModel.DataAnnotations;
namespace <#=config.nameSpace#>
{    

    public class <#=config.TableName#>Model
    {
        <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#>
        public <#= column.CSharpType#><# if(column.CommonType.IsValueType && column.IsNullable){#>?<#}#> <#=column.ColumnName#> { get; set; }
        <#}#>
    }
}
<#+
    public class config
    {
        public static readonly string ConnectionString="Data Source=(local);Initial Catalog=AppDB;User ID=sa;Password=zhaoyun123!@#;";
        public static readonly string DbDatabase="AppDB";
        public static readonly string TableName="SysSample";
        public static readonly string nameSpace="App.Sys";
    }
#>

有一些通用的我建了一个类config，访问config只需要config.TableName即可

访问DbHelper.ttinclude，值需要DbHelper.***即可

所以同道理，通用的类我们可以建造 Common.ttinclude来完善模版生成库

OK。配置好之后，值需要展开Test.tt就可以看到Test.txt文件，文件生成情况如下

//------------------------------------------------------------------------------
// <auto-generated>
//     此代码由T4模板自动生成
//       生成时间 2014-03-03 17:34:45 by YmNets
//     对此文件的更改可能会导致不正确的行为，并且如果
//     重新生成代码，这些更改将会丢失。
// </auto-generated>
//------------------------------------------------------------------------------
using System;
using System.ComponentModel.DataAnnotations;
namespace App.Sys
{    

    public class SysSampleModel
    {
                public string Id { get; set; }
                public string Name { get; set; }
                public int? Age { get; set; }
                public DateTime? Bir { get; set; }
                public string Photo { get; set; }
                public string Note { get; set; }
                public DateTime? CreateTime { get; set; }

    }
}

非常快速，所以，你可以很快建立自己项目的模版文件了。

以上只是基础，我们更加关心的是更多的扩展，比如判断数据库类型啊等等，做逻辑处理，获取字段的长度做处理啊。

所以我给大家提供一个备注：下面这条语句可以得到表的结构

 <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#>
       <#}#> 

其中：

column.CSharpType              字段的类型

column.IsNullable                  是否为空

column.IsPrimaryKey             是否是主键

column.CharLength               字段的长度，如varchar(50)那么column.CharLength=50

column.ColumnName             字段的名称

样例：判断是否DataTime类型

<#if(column.CSharpType=="DateTime"){#>

<# } #>

一个小小的例子，我们就能看懂MVC的T4模版，并能熟练运用它