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
- 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
- 修改输出文件扩展名为.cs
<#@ output extension=".cs" #>
- 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" #>
- 添加数据库操作DbHelper引用
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 #><#@ include file="$(ProjectDir)DbHelper.ttinclude" #>
DbHelper相对比较复杂，把一些常用操作进行了简单封装，因此放到一个单独的文件里面进行引用，可以方便的进行复用，这里DbHelper的后缀名使用ttinclude，这里的后缀名可以随便起，按照微软的建议：用于include的文件尽量不要使用.tt做后缀名
- 在页面底部定义一些常用变量，以方便操作
<#+ public class config { public static readonly string ConnectionString="Data Source=(local);Integrated Security=true;Initial Catalog=Northwind;"; public static readonly string DbDatabase="Northwind"; public static readonly string TableName="Customers"; } #>这里我们把数据库连接串和数据库、表名字定义一下，方便修改和使用
- 最后来编写用于实体类生成的代码
//------------------------------------------------------------------------------ // <auto-generated> // 此代码由T4模板自动生成 // 生成时间 <#=DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")#> by 懒惰的肥兔 // 对此文件的更改可能会导致不正确的行为，并且如果 // 重新生成代码，这些更改将会丢失。 // </auto-generated> //------------------------------------------------------------------------------ using System; namespace T4ConsoleApplication.Entities { public class <#=config.TableName#> { <# foreach(DbColumn column in DbHelper.GetDbColumns(config.ConnectionString, config.DbDatabase, config.TableName)){#> /// <summary> /// <#=column.Remark#> /// </summary> public <#= column.CSharpType#><# if(column.CommonType.IsValueType && column.IsNullable){#>?<#}#> <#=column.ColumnName#> { get; set; } <#}#> } }
- 全部完成后我们的Customers.tt文件就编写好了
Customers.tt
<#@ template debug="false" hostspecific="false" language="C#" #> <#@ output extension=".cs" #> <#@ assembly name="System.Core.dll" #> <#@ assembly name="System.Data.dll" #> <#@ assembly name="System.Data.DataSetExtensions.dll" #> <#@ assembly name="System.Xml.dll" #> <#@ import namespace="System" #> <#@ import namespace="System.Xml" #> <#@ import namespace="System.Linq" #> <#@ import namespace="System.Data" #> <#@ import namespace="System.Data.SqlClient" #> <#@ import namespace="System.Collections.Generic" #> <#@ import namespace="System.IO" #> <#@ include file="$(ProjectDir)DbHelper.ttinclude" #> //------------------------------------------------------------------------------ // <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
Customers.cs
//------------------------------------------------------------------------------ // <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。。。