MVC ---- DBHelper.ttinclude

　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

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, ) { 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; }

    }

}

原文：http://www.cnblogs.com/lzrabbit/archive/2012/07/18/2597953.html

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