你的位置:首页 > ASP.net教程

[ASP.net教程]T4模板根据DB生成实体类


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 T4语法快速入门。

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<Block> blocks = new List<Block>();  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;      }    }  }}#>

ModelAuto.ttinclude
<#@ template debug="true" hostspecific="true" language="C#" #><#@ output extension=".cs" #><#@ assembly name="System.Data" #><#@ assembly name="System.Data.OracleClient" #><#@ assembly name="System." #><#@ import namespace="System" #><#@ import namespace="System." #><#@ 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<string> 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{  /// <summary>  /// 数据表实体类:<#= tableName #>   /// </summary>  [Serializable()]  public class <#= tableName #>  {<#foreach(DataRow row in table.Rows){#>    /// <summary>    /// <#=row["备注"]#>    /// </summary>      public <#= manager.TransFromSqlType(row["数据类型"].ToString())#> <#=row["字段名"]#>{ get; set; }<#}#>  }}<# manager2.EndBlock(); #><#  }  #>    <# manager2.Process(true); #><#+  public class ModelManager  {    /// <summary>    /// 数据库连接字符串    /// </summary>    private const string CONNECTION_STRING = "Data Source=orcl;Persist Security Info=True;User ID=jjmis;Password=jjmis;Unicode=True";    /// <summary>    /// 用户信息表名    /// </summary>    private const string PERSONINFO_TABLE_NAME = "USERINFO";    /// <summary>    /// 根据表名查询表结构信息    /// </summary>    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}'"; /// <summary> /// 获得数据连接 /// </summary> /// <returns></returns> private OracleConnection GetConnection() { return new OracleConnection(CONNECTION_STRING); } /// <summary> /// 得到当前用户的所有表名 /// </summary> /// <returns></returns> public List<string> GetTableList() { string sql = "SELECT * FROM USER_TABLES"; DataTable dt = OracleHelper.ExecuteDataTable(sql); List<string> list = new List<string>(); 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; } /// <summary> /// 释放连接 /// </summary> /// <param name="con"></param> 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; } /// <summary> /// SQL[不完善,需要的自己改造] /// </summary> /// <param name="type"></param> /// <returns></returns> public string TransFromSqlType(string type) { if (string.IsNullOrEmpty(type)) { return string.Empty; } if (string.Equals(type, "number", StringComparison.OrdinalIgnoreCase)) { return "int"; } if (string.Equals(type, "date", StringComparison.OrdinalIgnoreCase)) { return "DateTime"; } else if (string.Equals(type, "nvarchar2", StringComparison.OrdinalIgnoreCase)) { return "string"; } return "string"; } }#><#+ public class OracleHelper { private static string oracleConnectionStr = "Data Source=orcl;Persist Security Info=True;User ID=jjmis;Password=jjmis;Unicode=True"; public static DataTable ExecuteDataTable(string sql, params OracleParameter[] paramList) { using (OracleConnection conn = new OracleConnection(oracleConnectionStr)) { conn.Open(); using (OracleCommand command = conn.CreateCommand()) { command.CommandText = sql; command.Parameters.AddRange(paramList); DataTable dt = new DataTable(); OracleDataAdapter adapter = new OracleDataAdapter(command); adapter.Fill(dt); return dt; } } } public static int ExecuteNonQuery(string sql, params OracleParameter[] paramList) { using (OracleConnection conn = new OracleConnection(oracleConnectionStr)) { conn.Open(); using (OracleCommand command = conn.CreateCommand()) { command.CommandText = sql; command.Parameters.AddRange(paramList); return command.ExecuteNonQuery(); } } } public static object ExecuteScalar(string sql, params OracleParameter[] paramList) { using (OracleConnection conn = new OracleConnection(oracleConnectionStr)) { conn.Open(); using (OracleCommand command = conn.CreateCommand()) { command.CommandText = sql; command.Parameters.AddRange(paramList); return command.ExecuteScalar(); } } } } #>

 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." #><#@ 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   {    /// <summary>    /// 数据表实体类:<#= row["TABLE_NAME"].ToString() #>     /// </summary>    [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);      #>       /// <summary>      /// <#= dc.DataType.Name #>:<#=ds2.Tables[0].Rows[0].ItemArray[2]#>      /// </summary>                  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。

文章中的源代码在此次下载

 

1.T4语法快速入门

2.T4模板根据DB生成实体类