编辑:您不必为每个对象实现 IFormattable ......那将是一个 PITA,严重限制和相当大的维护负担。只需将 Reflection 和 IFormatProvider 与 ICustomFormatter 一起使用,它就可以与任何对象一起使用。String.Format 有一个重载,可以将其作为参数。
我以前从来没有想过这个,但是你让我很感兴趣——所以我不得不快速旋转一下。请注意,我选择允许将额外的格式字符串传递给属性值,并且它仅适用于非索引和可访问的属性(尽管您可以轻松添加它)。
public class ReflectionFormatProvider : IFormatProvider, ICustomFormatter {
public object GetFormat(Type formatType) {
return formatType == typeof(ICustomFormatter) ? this : null;
}
public string Format(string format, object arg, IFormatProvider formatProvider) {
string[] formats = (format ?? string.Empty).Split(new char[] { ':' }, 2);
string propertyName = formats[0].TrimEnd('}');
string suffix = formats[0].Substring(propertyName.Length);
string propertyFormat = formats.Length > 1 ? formats[1] : null;
PropertyInfo pi = arg.GetType().GetProperty(propertyName);
if (pi == null || pi.GetGetMethod() == null) {
// Pass thru
return (arg is IFormattable) ?
((IFormattable)arg).ToString(format, formatProvider)
: arg.ToString();
}
object value = pi.GetGetMethod().Invoke(arg, null);
return (propertyFormat == null) ?
(value ?? string.Empty).ToString() + suffix
: string.Format("{0:" + propertyFormat + "}", value);
}
}
以及您稍作修改的示例:
var p1 = new Person() {Name="John", NumberOfCats=0, TimeTheyWillDie=DateTime.Today};
var p2 = new Person() {Name="Mary", NumberOfCats=50, TimeTheyWillDie=DateTime.MaxValue};
var str = string.Format(
new ReflectionFormatProvider(),
@"{0:Name} has {0:NumberOfCats} cats and {1:Name} has {1:NumberOfCats} cats.
They will die {0:TimeTheyWillDie:MM/dd/yyyy} and {1:TimeTheyWillDie} respectively.
This is a currency: {2:c2}.",
p1,
p2,
8.50M
);
Console.WriteLine(str);
输出:
John has 0 cats and Mary has 50 cats.
They will die 12/10/2008 and 12/31/9999 11:59:59 PM respectively.
This is a currency: $8.50.