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T4模板根据DB生成实体类

2018-06-17 21:49:37来源：未知阅读 ()

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 B
WHERE a.COLUMN_NAME = b.column_name
AND A.Table_Name = B.Table_Name
AND 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.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<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.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 
    {
        /// <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);
#>