自定义格式化字符串

 1 public class Vector : IFormattable
 2     {
 3         public double X { get; set; }
 4         public double Y { get; set; }
 5         public double Z { get; set; }
 6 
 7         public double Norm()
 8         {
 9             return X * X + Y * Y + Z * Z;
10         }
11 
12         public override string ToString()
13         {
14             return "(" + X + "," + Y + "," + Z + ")";
15         }
16 
17         public string ToString(string format, IFormatProvider formatProvider)
18         {
19             if (format == null)
20             {
21                 return ToString();
22             }
23 
24             string formatUpper = format.ToUpper();
25 
26             switch (formatUpper)
27             {
28                 case "N":
29                     return "|| " + Norm().ToString() + " ||";
30                 case "VE":
31                     return string.Format("({0:E},{1:E},{2:E})", X, Y, Z);
32                 case "IJK":
33                     var sb = new StringBuilder(X.ToString(), 30);
34                     sb.AppendFormat(" i + ");
35                     sb.AppendFormat(Y.ToString());
36                     sb.AppendFormat(" j + ");
37                     sb.AppendFormat(Z.ToString());
38                     sb.AppendFormat(" k");
39                     return sb.ToString();
40                 default:
41                     return ToString();
42             }
43         }
44     }

1 static void Main(string[] args)
2         {
3             Vector vector1 = new Vector { X = 3, Y = 4, Z = 5 };
4             Vector vector2 = new Vector { X = 5, Y = 4, Z = 3 };
5             Console.WriteLine("In IJK format, v1 is {0,10:IJK},V2 is {1,10:IJK}", vector1, vector2);
6 
7             
8             Console.ReadKey();
9         }