T4模版引擎之生成数据库实体类

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

　　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

   DbHelper.ttinclude

   <#+
    public class DbHelper
    {
    #region GetDbTables
    
    public static List 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().Select(row => new DbTable
    {
    TableName = row.Field("tablename"),
    SchemaName = row.Field("schemname"),
    Rows = row.Field("rows"),
    HasPrimaryKey = row.Field("HasPrimaryKey")
    }).ToList();
    }
    #endregion
   
    #region GetDbColumns
    
    public static List 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().Select(row => new DbColumn()
    {
    ColumnID = row.Field("ColumnID"),
    IsPrimaryKey = row.Field("IsPrimaryKey"),
    ColumnName = row.Field("ColumnName"),
    ColumnType = row.Field("ColumnType"),
    IsIdentity = row.Field("IsIdentity"),
    IsNullable = row.Field("IsNullable"),
    ByteLength = row.Field("ByteLength"),
    CharLength = row.Field("CharLength"),
    Scale = row.Field("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
    /// 
   
    /// 表结构
    /// 
    public sealed class DbTable
    {
    /// 
   
    /// 表名称
    /// 
    public string TableName { get; set; }
    /// 
   
    /// 表的架构
    /// 
    public string SchemaName { get; set; }
    /// 
   
    /// 表的记录数
    /// 
    public int Rows { get; set; }
   
    /// 
   
    /// 是否含有主键
    /// 
    public bool HasPrimaryKey { get; set; }
    }
    #endregion
   
    #region DbColumn
    /// 
   
    /// 表字段结构
    /// 
    public sealed class DbColumn
    {
    /// 
   
    /// 字段ID
    /// 
    public int ColumnID { get; set; }
   
    /// 
   
    /// 是否主键
    /// 
    public bool IsPrimaryKey { get; set; }
   
    /// 
   
    /// 字段名称
    /// 
    public string ColumnName { get; set; }
   
    /// 
   
    /// 字段类型
    /// 
    public string ColumnType { get; set; }
   
    /// 
   
    /// 数据库类型对应的C#类型
    /// 
    public string CSharpType
    {
    get
    {
    return SqlServerDbTypeMap.MapCsharpType(ColumnType);
    }
    }
   
    /// 
   
    /// 
    /// 
    public Type CommonType
    {
    get
    {
    return SqlServerDbTypeMap.MapCommonType(ColumnType);
    }
    }
   
    /// 
   
    /// 字节长度
    /// 
    public int ByteLength { get; set; }
   
    /// 
   
    /// 字符长度
    /// 
    public int CharLength { get; set; }
   
    /// 
   
    /// 小数位
    /// 
    public int Scale { get; set; }
   
    /// 
   
    /// 是否自增列
    /// 
    public bool IsIdentity { get; set; }
   
    /// 
   
    /// 是否允许空
    /// 
    public bool IsNullable { get; set; }
   
    /// 
   
    /// 描述
    /// 
    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

   //------------------------------------------------------------------------------
   // 
   // 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。
   // 
   //------------------------------------------------------------------------------
   
   using System;
   namespace T4ConsoleApplication.Entities
   { 
   
    public class <#=config.TableName#>
    {
    <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#>
   
    /// 
   
    /// <#=column.Remark#>
    /// 
    
    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

   Customers.tt

   <#@ 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" #>
   //------------------------------------------------------------------------------
   // 
   // 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。
   // 
   //------------------------------------------------------------------------------
   
   using System;
   namespace T4ConsoleApplication.Entities
   { 
   
    public class <#=config.TableName#>
    {
    <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#>
   
    /// 
   
    /// <#=column.Remark#>
    /// 
    
    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

   Customers.cs

   //------------------------------------------------------------------------------
   // 
   // 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。
   // 
   //------------------------------------------------------------------------------
   
   using System;
   namespace T4ConsoleApplication.Entities
   { 
   
    public class Customers
    {
    
    /// 
   
    /// 
    /// 
    
    public string CustomerID { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string CompanyName { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string ContactName { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string ContactTitle { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string Address { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string City { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string Region { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string PostalCode { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string Country { get; set; }
    
    /// 
   
    /// 
    /// 
    
    public string Phone { get; set; }
    
    /// 
   
    /// 
    /// 
    
    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。

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