1.前言
为什么会有这篇文章了，最近看到了一些框架，里面要写的代码太多了，故此就想偷懒，要是能写出一个T4模板，在数据库添加表后，根据模板就可以自动生成了类文件了，这样多好，心动不如行动。记得使用T4模板还是2年前，那个时候听波波老师讲课做我们的最后一个大项目CRM,简简单单的写了一下模板，保存一下，所有的类文件就出来了，当时那个膜拜，油然而生。
同时在工作中，我们公司自己开发的一个ORM，实体类都要自己写，一个数据库表的字段太多，写的真是手抽筋。如果你对T4基础语法不是很了解，可以参考我前面写的一篇文章 。
2.原理
我们要做的事情是通过数据库表生成实体类。
第一步 我们要查询出当前用户下的所有数据库表。
第二步 查询出数据库表的结构，比如字段的名称，字段的类型，字段的长度大小，是否为空等等。
工作中oracle用的比较多，在这里我就分析oracle和mssql
3.oracle
查询当前用户所有的表。
SELECT TABLE_NAME FROM USER_TABLES;
根据表名查询表结构数据
SELECT A.column_name 字段名, A.data_type 数据类型,A.data_length 长度,A.data_precision 整数位,A.Data_Scale 小数位,A.nullable 允许空值,A.Data_default 缺省值,B.comments 备注,A.TABLE_NAME 表名FROM user_tab_columns A, user_col_comments BWHERE a.COLUMN_NAME = b.column_nameAND A.Table_Name = B.Table_NameAND A.Table_Name = 'AFFIXINFO'
ModelAuto.ttinclude来源与网上，作用是生成一个一个单独的类文件，即xx.cs文件。
<#@ assembly name="System.Core"#><#@ assembly name="EnvDTE"#><#@ import namespace="System.Collections.Generic"#><#@ import namespace="System.IO"#><#@ import namespace="System.Text"#><#@ import namespace="Microsoft.VisualStudio.TextTemplating"#><#+class Manager{ public struct Block { public String Name; public int Start, Length; } public List blocks = new List (); public Block currentBlock; public Block footerBlock = new Block(); public Block headerBlock = new Block(); public ITextTemplatingEngineHost host; public ManagementStrategy strategy; public StringBuilder template; public String OutputPath { get; set; } public Manager(ITextTemplatingEngineHost host, StringBuilder template, bool commonHeader) { this.host = host; this.template = template; OutputPath = String.Empty; strategy = ManagementStrategy.Create(host); } public void StartBlock(String name) { currentBlock = new Block { Name = name, Start = template.Length }; } public void StartFooter() { footerBlock.Start = template.Length; } public void EndFooter() { footerBlock.Length = template.Length - footerBlock.Start; } public void StartHeader() { headerBlock.Start = template.Length; } public void EndHeader() { headerBlock.Length = template.Length - headerBlock.Start; } public void EndBlock() { currentBlock.Length = template.Length - currentBlock.Start; blocks.Add(currentBlock); } public void Process(bool split) { String header = template.ToString(headerBlock.Start, headerBlock.Length); String footer = template.ToString(footerBlock.Start, footerBlock.Length); blocks.Reverse(); foreach(Block block in blocks) { String fileName = Path.Combine(OutputPath, block.Name); if (split) { String content = header + template.ToString(block.Start, block.Length) + footer; strategy.CreateFile(fileName, content); template.Remove(block.Start, block.Length); } else { strategy.DeleteFile(fileName); } } }}class ManagementStrategy{ internal static ManagementStrategy Create(ITextTemplatingEngineHost host) { return (host is IServiceProvider) ? new VSManagementStrategy(host) : new ManagementStrategy(host); } internal ManagementStrategy(ITextTemplatingEngineHost host) { } internal virtual void CreateFile(String fileName, String content) { File.WriteAllText(fileName, content); } internal virtual void DeleteFile(String fileName) { if (File.Exists(fileName)) File.Delete(fileName); }}class VSManagementStrategy : ManagementStrategy{ private EnvDTE.ProjectItem templateProjectItem; internal VSManagementStrategy(ITextTemplatingEngineHost host) : base(host) { IServiceProvider hostServiceProvider = (IServiceProvider)host; if (hostServiceProvider == null) throw new ArgumentNullException("Could not obtain hostServiceProvider"); EnvDTE.DTE 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); } internal override void CreateFile(String fileName, String content) { base.CreateFile(fileName, content); ((EventHandler)delegate { templateProjectItem.ProjectItems.AddFromFile(fileName); }).BeginInvoke(null, null, null, null); } internal override void DeleteFile(String fileName) { ((EventHandler)delegate { FindAndDeleteFile(fileName); }).BeginInvoke(null, null, null, null); } private void FindAndDeleteFile(String fileName) { foreach(EnvDTE.ProjectItem projectItem in templateProjectItem.ProjectItems) { if (projectItem.get_FileNames(0) == fileName) { projectItem.Delete(); return; } } }}#> <#@ template debug="true" hostspecific="true" language="C#" #><#@ output extension=".cs" #><#@ assembly name="System.Data" #><#@ assembly name="System.Data.OracleClient" #><#@ assembly name="System.Xml" #><#@ import namespace="System" #><#@ import namespace="System.Xml" #><#@ import namespace="System.Data" #><#@ import namespace="System.Data.OracleClient" #><#@ import namespace="System.Collections.Generic"#><#@ include file="ModelAuto.ttinclude"#><# var manager2 = new Manager(Host, GenerationEnvironment, true) { OutputPath = Path.GetDirectoryName(Host.TemplateFile)}; #><# ModelManager manager = new ModelManager();List list=manager.GetTableList();#><# foreach (var item in list) { string tableName=item; DataTable table= manager.GetTableSchema(tableName); #> <# manager2.StartBlock(tableName+".cs"); #>using System;using System.Data;using System.Data.OracleClient;namespace Model{ /// /// 数据表实体类：<#= tableName #> /// [Serializable()] public class <#= tableName #> {<#foreach(DataRow row in table.Rows){#> /// /// <#=row["备注"]#> /// public <#= manager.TransFromSqlType(row["数据类型"].ToString())#> <#=row["字段名"]#>{ get; set; }<#}#> }}<# manager2.EndBlock(); #><# } #> <# manager2.Process(true); #><#+ public class ModelManager { /// /// 数据库连接字符串 /// private const string CONNECTION_STRING = "Data Source=orcl;Persist Security Info=True;User ID=jjmis;Password=jjmis;Unicode=True"; /// /// 用户信息表名 /// private const string PERSONINFO_TABLE_NAME = "USERINFO"; /// /// 根据表名查询表结构信息 /// private const string SELECT_SCHEMA_BY_TABLE_NAME = @"SELECT A.column_name 字段名, A.data_type 数据类型, A.data_length 长度, A.data_precision 整数位, A.Data_Scale 小数位, A.nullable 允许空值, A.Data_default 缺省值, B.comments 备注, A.TABLE_NAME 表名 FROM user_tab_columns A, user_col_comments B WHERE a.COLUMN_NAME = b.column_name AND A.Table_Name = B.Table_Name AND A.Table_Name = '{0}'"; /// /// 获得数据连接 /// /// /// 得到当前用户的所有表名 /// /// GetTableList() { string sql = "SELECT * FROM USER_TABLES"; DataTable dt = OracleHelper.ExecuteDataTable(sql); List list = new List (); if (dt!=null&&dt.Rows.Count>0) { for (int i = 0; i < dt.Rows.Count; i++) { list.Add(dt.Rows[i]["TABLE_NAME"].ToString()); } } return list; } /// /// 释放连接 /// /// private void ReleaseConnection(OracleConnection con) { if (con != null) { if (con.State == ConnectionState.Open) { con.Close(); } } } public DataTable GetTableSchema(string tableName) { DataTable dt; using (OracleConnection con = GetConnection()) { con.Open(); OracleCommand cmd = con.CreateCommand(); cmd.CommandText = string.Format(SELECT_SCHEMA_BY_TABLE_NAME,tableName); cmd.CommandType = CommandType.Text; OracleDataAdapter adapter = new OracleDataAdapter(cmd); DataSet ds = new DataSet(); adapter.Fill(ds); dt = ds.Tables[0]; } return dt; } /// /// SQL[不完善,需要的自己改造] /// /// /// 保存此模板文件就可以生成下面类文件。
4.Mssql
查询数据库表
string connectionString = "Data Source=.;Initial Catalog=NFineBase;User ID=sa;Password=hjf19870810;"; SqlConnection conn = new SqlConnection(connectionString); conn.Open(); System.Data.DataTable schema = conn.GetSchema("TABLES"); 通过数据库表查询表结构
SELECT 表名=sobj.name,字段名=scol.name,字段说明=sprop.[value] FROM syscolumns as scol inner join sys.sysobjects as sobj on scol.id=sobj.id and sobj.xtype='U' and sobj.name<>'dtproperties' left join sys.extended_properties as sprop on scol.id=sprop.major_id and scol.colid=sprop.minor_id where sobj.name='@tableName' and scol.name='@columnName'
同样我们要生成多个类文件，需要引入 ModelAuto.ttinclude
ModelTemplate.tt文件如下
<#@ template language="C#" debug="True" hostspecific="True" #><#@ output extension=".cs" #><#@ assembly name="System.Data" #><#@ assembly name="System.xml" #><#@ import namespace="System.Collections.Generic" #><#@ import namespace="System.Data.SqlClient" #><#@ import namespace="System.Data" #><#@ include file="ModelAuto.ttinclude"#><# var manager = new Manager(Host, GenerationEnvironment, true) { OutputPath = Path.GetDirectoryName(Host.TemplateFile)}; #><# string connectionString = "Data Source=.;Initial Catalog=NFineBase;User ID=sa;Password=hjf19870810;"; SqlConnection conn = new SqlConnection(connectionString); conn.Open(); System.Data.DataTable schema = conn.GetSchema("TABLES"); string selectQuery = "select * from @tableName"; SqlCommand command = new SqlCommand(selectQuery,conn); SqlDataAdapter ad = new SqlDataAdapter(command); System.Data.DataSet ds = new DataSet(); string propQuery = "SELECT 表名=sobj.name,字段名=scol.name,字段说明=sprop.[value] FROM syscolumns as scol inner join sys.sysobjects as sobj on scol.id=sobj.id and sobj.xtype='U' and sobj.name<>'dtproperties' left join sys.extended_properties as sprop on scol.id=sprop.major_id and scol.colid=sprop.minor_id where sobj.name='@tableName' and scol.name='@columnName'"; SqlCommand command2 = new SqlCommand(propQuery,conn); SqlDataAdapter ad2 = new SqlDataAdapter(command2); System.Data.DataSet ds2 = new DataSet(); #><# foreach(System.Data.DataRow row in schema.Rows) { #> <# manager.StartBlock(row["TABLE_NAME"]+".cs"); #> //----------<#=row["TABLE_NAME"].ToString()#>开始---------- using System; namespace MyProject.Entities { /// /// 数据表实体类：<#= row["TABLE_NAME"].ToString() #> /// [Serializable()] public class <#= row["TABLE_NAME"].ToString() #> { <# ds.Tables.Clear(); command.CommandText = selectQuery.Replace("@tableName",row["TABLE_NAME"].ToString()); ad.FillSchema(ds, SchemaType.Mapped, row["TABLE_NAME"].ToString()); foreach (DataColumn dc in ds.Tables[0].Columns) { #> <# ds2.Tables.Clear(); command2.CommandText = propQuery.Replace("@tableName",row["TABLE_NAME"].ToString()); command2.CommandText = command2.CommandText.Replace("@columnName",dc.ColumnName); ad2.Fill(ds2); #> /// /// <#= dc.DataType.Name #>:<#=ds2.Tables[0].Rows[0].ItemArray[2]#> /// public <#= dc.DataType.Name #> <#= dc.ColumnName #> { get;set;} <# } #> } } //----------<#=row["TABLE_NAME"].ToString()#>结束---------- <# manager.EndBlock(); #><# } #> <# manager.Process(true);#> 保存ModelTemplate.tt就可以得到类文件。
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