為什麼叫T4？因為簡寫為4個T。 T4(Text Template Transformation Toolkit)是微軟官方在VisualStudio 2008中開始使用的代碼生成引擎。在 Visual Studio 中，“T4 文本模板”是由一些文本塊和控制邏輯組成的混合模板，它可以生成文本文件。 ...
為什麼叫T4？因為簡寫為4個T。
T4(Text Template Transformation Toolkit)是微軟官方在VisualStudio 2008中開始使用的代碼生成引擎。在 Visual Studio 中，“T4 文本模板”是由一些文本塊和控制邏輯組成的混合模板，它可以生成文本文件。 在 Visual C# 或 Visual Basic 中，控制邏輯編寫為程式代碼的片段。生成的文件可以是任何類型的文本，例如網頁、資源文件或任何語言的程式源代碼。現在的VS中只要與代碼生成相關的場景基本上都能找T4的身影，比如MVC的視圖模板，Entity Framwork的DataContext模板等等。
若論靈活性，各種代碼生成工具還真不如T4模板。
在VS2013種預設沒有了T4模板，取而代之的是文本模板，但是他們的尾碼名都是.tt。我們可以通過NuGet安裝T4模板。
安裝之後，我們在項目中新建項的時候，在VS模板中就多了兩項和T4模板相關的模板。
當我們在新建的T4模板中進行代碼編寫的時候，預設是沒有智能提示的，我們需要再安裝一個T4Editor的VS插件tangibleT4EditorPlusModellingToolsVS2013.msi。
下載地址:
由於我這裡用的是VS2013，所以按照13的插件，安裝插件時先關閉VS，安裝完成之後在T4模板中編寫代碼時就有了智能提示了。
關於T4模板的詳細講解，大家可以參照一下博客文章：
（譯）理解 T4 模板：<#@ parameter #> 指令
我這裡要說的是，如何在項目中替代其它的代碼工具來使用，比如說，自動生成資料庫中的POCO類。
思路：1、我們要查詢中資料庫中的表和欄位。2、根據數據表名才，將其生成多個POCO類文件
How to do？
開發環境：VS2013
準備工作：添加必須的程式集引用
在自己電腦上面用everythin找到Microsoft.VisualStudio.TextTemplating.Interfaces.10.0.dll，然後添加引用，如果沒有，你就網上下載一個。
方式一
1、添加一個T4模板文件DbHelper，將其尾碼修改為.ttinclude，因為我是將其作為內嵌的T4文件，不修改擴展名的話，會將其當成T4模板文件進行生成。
<#+
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>
/// 表結構
/// </summary>
public sealed class DbTable
{
/// <summary>
/// 表名稱
/// </summary>
public string TableName { get; set; }
/// <summary>
/// 表的架構
/// </summary>
public string SchemaName { get; set; }
/// <summary>
/// 表的記錄數
/// </summary>
public int Rows { get; set; }
/// <summary>
/// 是否含有主鍵
/// </summary>
public bool HasPrimaryKey { get; set; }
}
#endregion
#region DbColumn
/// <summary>
/// 表欄位結構
/// </summary>
public sealed class DbColumn
{
/// <summary>
/// 欄位ID
/// </summary>
public int ColumnID { get; set; }
/// <summary>
/// 是否主鍵
/// </summary>
public bool IsPrimaryKey { get; set; }
/// <summary>
/// 欄位名稱
/// </summary>
public string ColumnName { get; set; }
/// <summary>
/// 欄位類型
/// </summary>
public string ColumnType { get; set; }
/// <summary>
/// 資料庫類型對應的C#類型
/// </summary>
public string CSharpType
{
get
{
return SqlServerDbTypeMap.MapCsharpType(ColumnType);
}
}
/// <summary>
///
/// </summary>
public Type CommonType
{
get
{
return SqlServerDbTypeMap.MapCommonType(ColumnType);
}
}
/// <summary>
/// 位元組長度
/// </summary>
public int ByteLength { get; set; }
/// <summary>
/// 字元長度
/// </summary>
public int CharLength { get; set; }
/// <summary>
/// 小數位
/// </summary>
public int Scale { get; set; }
/// <summary>
/// 是否自增列
/// </summary>
public bool IsIdentity { get; set; }
/// <summary>
/// 是否允許空
/// </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
#>
View Code
上面的代碼就是查詢資料庫中的表和欄位。
2、同樣添加另一個T4模板文件，並修改尾碼名Manager.ttinclude
<#@ assembly name="System.Data.Linq" #><#@ assembly name="EnvDTE" #><#@ assembly name="System.Xml" #><#@ assembly name="System.Xml.Linq" #><#@ import namespace="System.Collections.Generic" #><#@ import namespace="System.IO" #><#@ import namespace="System.Text" #><#@ import namespace="Microsoft.VisualStudio.TextTemplating" #><#+ // https://raw.github.com/damieng/DamienGKit // http://damieng.com/blog/2009/11/06/multiple-outputs-from-t4-made-easy-revisited // Manager class records the various blocks so it can split them up class Manager { private class Block { public String Name; public int Start, Length; public bool IncludeInDefault; } private Block currentBlock; private readonly List<Block> files = new List<Block>(); private readonly Block footer = new Block(); private readonly Block header = new Block(); private readonly ITextTemplatingEngineHost host; private readonly StringBuilder template; protected readonly List<String> generatedFileNames = new List<String>(); public static Manager Create(ITextTemplatingEngineHost host, StringBuilder template) { return (host is IServiceProvider) ? new VSManager(host, template) : new Manager(host, template); } public void StartNewFile(String name) { if (name == null) throw new ArgumentNullException("name"); CurrentBlock = new Block { Name = name }; } public void StartFooter(bool includeInDefault = true) { CurrentBlock = footer; footer.IncludeInDefault = includeInDefault; } public void StartHeader(bool includeInDefault = true) { CurrentBlock = header; header.IncludeInDefault = includeInDefault; } public void EndBlock() { if (CurrentBlock == null) return; CurrentBlock.Length = template.Length - CurrentBlock.Start; if (CurrentBlock != header && CurrentBlock != footer) files.Add(CurrentBlock); currentBlock = null; } public virtual void Process(bool split, bool sync = true) { if (split) { EndBlock(); String headerText = template.ToString(header.Start, header.Length); String footerText = template.ToString(footer.Start, footer.Length); String outputPath = Path.GetDirectoryName("host.TemplateFile"); files.Reverse(); if (!footer.IncludeInDefault) template.Remove(footer.Start, footer.Length); foreach(Block block in files) { String fileName = Path.Combine(outputPath, block.Name); String content = headerText + template.ToString(block.Start, block.Length) + footerText; generatedFileNames.Add(fileName); CreateFile(fileName, content); template.Remove(block.Start, block.Length); } if (!header.IncludeInDefault) template.Remove(header.Start, header.Length); } } protected virtual void CreateFile(String fileName, String content) { if (IsFileContentDifferent(fileName, content)) File.WriteAllText(fileName, content); } public virtual String GetCustomToolNamespace(String fileName) { return null; } public virtual String DefaultProjectNamespace { get { return null; } } protected bool IsFileContentDifferent(String fileName, String newContent) { return !(File.Exists(fileName) && File.ReadAllText(fileName) == newContent); } private Manager(ITextTemplatingEngineHost host, StringBuilder template) { this.host = host; this.template = template; } private Block CurrentBlock { get { return currentBlock; } set { if (CurrentBlock != null) EndBlock(); if (value != null) value.Start = template.Length; currentBlock =
