.Net关于几种格式化字符串

在.Net中将一个对象格式化为字符串有以下方式:
1,String.Format(string format, params object[] args)以及几种变形
     这种格式化要求args能实现了IFormattable接口
2,string Format(IFormatProvider provider, string format, params object[] args)
     这种格式化要求提供一个自定义的格式化功能
3,Object.ToString()
     众所周知的,调用了虚方法

下面例子可以显示这几种格式化功能的具体使用时机与实现方法
加入我们要格式化手机号码,众所周知,手机号码是11位的连续整数,但是有时候需要用139-2212-0987的格式进行显示,下面具体的代码:
首先是3个类,公共完成格式化功能:

 

        class ModilePhone:IFormattable        {            public string phone = "15115226678";            string IFormattable.ToString(string format, IFormatProvider formatProvider)            {                if (formatProvider == null)                    formatProvider = System.Globalization.CultureInfo.CurrentCulture;                if (format == "G")                    return string.Format("From IFormattable[G]:{0}", phone);                return phone;                            }            public override string ToString()            {                return "From ToString();";            }        }        class ModilePhoneFormatter : ICustomFormatter        {            string ICustomFormatter.Format(string format, object arg, IFormatProvider formatProvider)            {                ModilePhone tmp = arg as ModilePhone;                if (tmp == null) throw new ArgumentException(string.Format("ModilePhoneFormatter不支持{0}类型的",arg.GetType()));                if (format == "NNN-NNNN-NNNN")                    return string.Format("From ICustomFormatter:{0}{1}{2}-{3}{4}{5}{6}-{7}{8}{9}{10}",                                            tmp.phone[0], tmp.phone[1], tmp.phone[2],                                           tmp.phone[3], tmp.phone[4], tmp.phone[5], tmp.phone[6],                                           tmp.phone[7], tmp.phone[8], tmp.phone[9], tmp.phone[10]                                        );                return "";            }        }        class ModilePhoneFormatProvider : IFormatProvider        {            object IFormatProvider.GetFormat(Type formatType)            {                if (formatType == typeof(ICustomFormatter))                    return new ModilePhoneFormatter();                else                    return null;            }        }

  

下面是调用的例子:
           

     ModilePhone tmp = new ModilePhone();     string str0 = string.Format(new ModilePhoneFormatProvider(), "{0:NNN-NNNN-NNNN}", tmp);      //str0 : From ICustomFormatter:151-1522-6678     string str1 = string.Format("{0:G}", tmp);     //str1 : From IFormattable[G]:15115226678     string str2 = tmp.ToString();     //str2 : //From ToString();