[转]T4模版引擎之生成数据库实体类

本文转自：http://www.cnblogs.com/lzrabbit/archive/2012/07/18/2597953.html

在通过T4模版引擎之基础入门 对T4有了初步印象后，我们开始实战篇。T4模板引擎可以当做一个代码生成器，代码生成器的职责当然是用来生成代码(这不是废话吗)。而这其中我们使用的最普遍的是根据数据库生成实体类。

　　工欲善其事必先利其器，在这之前先来介绍一款T4编辑器T4 Editor，我们可以点击链接去下载然后安装，不过还是推荐大家直接在VS扩展管理器里直接安装来的方便 工具->扩展管理器->联机库 搜索 "T4 Editor"，选择第一项 "tangible T4 Editor 2.0 plus modeling tools for VS2010" 进行安装即可，如下图所示:

安装上T4 Editor后，编辑T4模板是就有代码着色和智能提示了，下图为安装T4 Editor后的代码着色效果，怎么样是不是耳目一新，呵呵

 

接下来开始正式进入我们的主题，从数据库自动生成实体类

1. 新建一个控制台项目，然后添加T4模板，这里我们起名字为Customers.tt

   

2. 修改输出文件扩展名为.cs

   <#@ output extension=".cs" #>

3. 添加常用的程序集和命名空间引用
   

   <#@ 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" #>

   
4. 添加数据库操作DbHelper引用
   

   <#+
       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
   
   #>

   

   <#@ include file="$(ProjectDir)DbHelper.ttinclude"  #>

   DbHelper相对比较复杂，把一些常用操作进行了简单封装，因此放到一个单独的文件里面进行引用，可以方便的进行复用，这里DbHelper的后缀名使用ttinclude，这里的后缀名可以随便起，按照微软的建议：用于include的文件尽量不要使用.tt做后缀名

5. 在页面底部定义一些常用变量，以方便操作
   

   <#+
       public class config
       {
           public static readonly string ConnectionString="Data Source=(local);Integrated Security=true;Initial Catalog=Northwind;";
           public static readonly string DbDatabase="Northwind";
           public static readonly string TableName="Customers";
       }
   #>

   

   这里我们把数据库连接串和数据库、表名字定义一下，方便修改和使用

6. 最后来编写用于实体类生成的代码
   

   //------------------------------------------------------------------------------
   // <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 懒惰的肥兔
   //     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;
   namespace T4ConsoleApplication.Entities
   {    
   
       public class <#=config.TableName#>
       {
           <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#>
   
           /// <summary>
           /// <#=column.Remark#>
           /// </summary>
           public <#= column.CSharpType#><# if(column.CommonType.IsValueType && column.IsNullable){#>?<#}#> <#=column.ColumnName#> { get; set; }
           <#}#> 
   
       }
   }

   
7. 全部完成后我们的Customers.tt文件就编写好了
   

   <#@ template debug="false" hostspecific="false" language="C#" #>
   <#@ output extension=".cs" #>
   <#@ 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 懒惰的肥兔
   //     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;
   namespace T4ConsoleApplication.Entities
   {    
   
       public class <#=config.TableName#>
       {
           <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#>
   
           /// <summary>
           /// <#=column.Remark#>
           /// </summary>
           public <#= column.CSharpType#><# if(column.CommonType.IsValueType && column.IsNullable){#>?<#}#> <#=column.ColumnName#> { get; set; }
           <#}#> 
   
       }
   }
   
   <#+
       public class config
       {
           public static readonly string ConnectionString="Data Source=(local);Integrated Security=true;Initial Catalog=Northwind;";
           public static readonly string DbDatabase="Northwind";
           public static readonly string TableName="Customers";
       }
   #>

   

   进行保存后会自动生成Customers.cs文件

   

   //------------------------------------------------------------------------------
   // <auto-generated>
   //     此代码由T4模板自动生成
   //       生成时间 2012-07-18 17:51:26 by 懒惰的肥兔
   //     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;
   namespace T4ConsoleApplication.Entities
   {    
   
       public class Customers
       {
   
           /// <summary>
           ///
           /// </summary>
           public string CustomerID { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string CompanyName { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string ContactName { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string ContactTitle { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string Address { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string City { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string Region { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string PostalCode { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string Country { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string Phone { get; set; }
   
           /// <summary>
           ///
           /// </summary>
           public string Fax { get; set; }
   
       }
   }

   

   　　至此完整演示了怎样一步步根据数据库生成实体类的操作，是不是很简单，如对语法和操作不理解的地方可以参考T4模版引擎之基础入门，稍微用心研究下，轻松打造属于自己的代码生成器。

　　本文简单介绍了基于单个模板生成数据库实体类的示例，离具体实用还有一定的距离，毕竟总不能为每个数据表建一个模板吧，下一篇将揭晓如何通过单个T4模板生成多个文件，以及自动生成整个数据库的所有实体类，敬请期待

　　下班了，拍拍屁股走人。。。

源码：T4ConsoleApplication.rar

注：此文章属懒惰的肥兔原创，版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文链接:http://www.cnblogs.com/lzrabbit/archive/2012/07/18/2597953.html

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