使用T4模板创建一个例子

1、创建项目，添加新项，名称处填写Messages.tt，如下图：

添加后，Messages.tt文件内容如下：

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ output extension=".txt" #>

2、创建一个实体对象MessageEntry，用以传递模版信息，具体代码如下：

    public class MessageEntry
    {
        public string Id { get; private set; }
        public string Value { get; private set; }
        public string Category { get; private set; }
        public MessageEntry(string id, string value, string category)
        {
            this.Id = id;
            this.Value = value;
            this.Category = category;
        }

        public string Format(params object[] args)
        {
            return string.Format(this.Value, args);
        }
    }

3、新建文件Messages.xml，用以配置要生成的信息：

<?xml version="1.0" encoding="utf-8" ?>
<messages>
    <message id="MandatoryField" value="The {0} is mandatory." category="Validation"/>
    <message id="GreaterThan" value="The {0} must be greater than {1}." category="Validation"/>
    <message id="ReallyDelete" value="Do you really want to delete the {0}." category="Confirmation"/>
    <message id="UserInfo" value="Do you really want to delete the {0}." category="UserItemInfo"/>
</messages>

4、修改Messages.tt文件如下：

<#@template debug="false" hostspecific="true" language="C#"#>
<#@assembly name="System.Core.dll"#>
<#@assembly name="System.Xml"#>
<#@import namespace="System"#>
<#@import namespace="System.Xml"#>
<#@import namespace="System.Linq"#>
<#@output extension=".cs" #>
namespace MessageCodeGenrator
{
    using System;
    public static class Messages
    {
        <# XmlDocument messageDoc = new XmlDocument();
            messageDoc.Load(this.Host.ResolvePath("Messages.xml"));
            var messageEntries = messageDoc.GetElementsByTagName("message").Cast<XmlElement>();
            var categories = (from element in messageEntries
                            select element.Attributes["category"].Value).Distinct();
            foreach (var category in categories)
            {#>

        public static class <#=  category#>
        {
            <#
            foreach (var element in messageDoc.GetElementsByTagName("message").Cast<XmlElement>().Where(element => element.Attributes["category"].Value == category))
            {
                string id = element.Attributes["id"].Value;
                string value = element.Attributes["value"].Value;
                string categotry = element.Attributes["category"].Value;
            #>

            public static MessageEntry <#= id #> = new MessageEntry("<#= id #>","<#= value#>","<#= categotry#>");
        <#}#>
}
    <#}#>
}
}

5、右键点击Messages.tt，选择运行自定义工具，如下：

6、执行完后，查看Messages.cs文件，可以看到已经生成了所需要的代码：

namespace MessageCodeGenrator
{
    using System;
    public static class Messages
    {
        
        public static class Validation
        {
            
            public static MessageEntry MandatoryField = new MessageEntry("MandatoryField","The {0} is mandatory.","Validation");
        
            public static MessageEntry GreaterThan = new MessageEntry("GreaterThan","The {0} must be greater than {1}.","Validation");
        }
    
        public static class Confirmation
        {
            
            public static MessageEntry ReallyDelete = new MessageEntry("ReallyDelete","Do you really want to delete the {0}.","Confirmation");
        }
    
        public static class UserItemInfo
        {
            
            public static MessageEntry UserInfo = new MessageEntry("UserInfo","Do you really want to delete the {0}.","UserItemInfo");
        }
    }
}