[C#]使用IFormattable接口来实现字符串格式化
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开发工具：VS2017
语言：C#
DotNet版本：.Net FrameWork 4.0及以上
一、编写一个Person类，代码如下：
class Person
{
public string FirstName { set; get; }
public string LastName { set; get; }
}并让Person类继承IFormattable，代码如下：
class Person:IFormattable
{
public string FirstName { set; get; }
public string LastName { set; get; }
public string ToString(string format, IFormatProvider formatProvider)
{
//关键代码，后面给出
}
}这里将会列出需要实现IFormattable的方法ToString(string format, IFormatProvider formatProvider)，这里是关键代码，用来格式字符串，暂时不给出，由后面给出。
二、编写 PersonFormatter类，让其继承IFormatProvider及ICustomFormatter，用于对字符串进行格式化，代码如下：
class PersonFormatter : IFormatProvider,ICustomFormatter
{
public string Format(string format, object arg, IFormatProvider formatProvider)
{
//Format实现代码
}
public object GetFormat(Type formatType)
{
//GetFormat实现代码
}
}Format：用于格式化字符串
Format的实现代码如下：
Person person = arg as Person;
switch(format)
{
case "CH":return $"{person.LastName} {person.FirstName}";
case "EN":return $"{person.FirstName} {person.LastName}";
default: return $"{person.LastName} {person.FirstName}";
}GetFormat的实现代码如下：
if (formatType == typeof(ICustomFormatter)) return this;
return null;因此，PersonFormatter类的代码如下：
class PersonFormatter : IFormatProvider,ICustomFormatter
{
public string Format(string format, object arg, IFormatProvider formatProvider)
{
Person person = arg as Person;
switch(format)
{
case "CH":return $"{person.LastName} {person.FirstName}";
case "EN":return $"{person.FirstName} {person.LastName}";
default: return $"{person.LastName} {person.FirstName}";
}
}
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomFormatter)) return this;
return null;
}
}三、实现Person类IFormattable接口ToString方法，代码如下：
ICustomFormatter customFormatter = formatProvider as ICustomFormatter;
if (customFormatter == null) return this.ToString();
return customFormatter.Format(format, this, null);最终Person类代码如下：
class Person:IFormattable
{
public string FirstName { set; get; }
public string LastName { set; get; }
public string ToString(string format, IFormatProvider formatProvider)
{
ICustomFormatter customFormatter = formatProvider as ICustomFormatter;
if (customFormatter == null) return this.ToString();
return customFormatter.Format(format, this, null);
}
}四、使用Peson类的ToString方法，编写以下代码：
Person p1 = new Person { FirstName = "XY", LastName = "CN" };
PersonFormatter pf = new PersonFormatter();
string s1 = p1.ToString("CN", pf);
Console.WriteLine(s1);
string s2 = p1.ToString("EN", pf);
Console.WriteLine(s2);五、运行结果：
六、附上完整源码：
class Program
{
static void Main(string[] args)
{
Person p1 = new Person { FirstName = "XY", LastName = "CN" };
PersonFormatter pf = new PersonFormatter();
string s1 = p1.ToString("CN", pf);
Console.WriteLine(s1);
string s2 = p1.ToString("EN", pf);
Console.WriteLine(s2);
}
}
class PersonFormatter : IFormatProvider,ICustomFormatter
{
public string Format(string format, object arg, IFormatProvider formatProvider)
{
Person person = arg as Person;
switch(format)
{
case "CH":return $"{person.LastName} {person.FirstName}";
case "EN":return $"{person.FirstName} {person.LastName}";
default: return $"{person.LastName} {person.FirstName}";
}
}
public object GetFormat(Type formatType)
{
if (formatType == typeof(ICustomFormatter)) return this;
return null;
}
}
class Person:IFormattable
{
public string FirstName { set; get; }
public string LastName { set; get; }
public string ToString(string format, IFormatProvider formatProvider)
{
ICustomFormatter customFormatter = formatProvider as ICustomFormatter;
if (customFormatter == null) return this.ToString();
return customFormatter.Format(format, this, null);
}
}本文参与 腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。
原始发表：2017-12-21 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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