如何：在结构间实现用户定义的转换（C# 编程指南）
本示例定义 RomanNumeral 和 BinaryNumeral 两个结构，并演示二者之间的转换。
示例
struct RomanNumeral
{
private int value;
public RomanNumeral(int value) //constructor
{
this.value = value;
}
static public implicit operator RomanNumeral(int value)
{
return new RomanNumeral(value);
}
static public implicit operator RomanNumeral(BinaryNumeral binary)
{
return new RomanNumeral((int)binary);
}
static public explicit operator int(RomanNumeral roman)
{
return roman.value;
}
static public implicit operator string(RomanNumeral roman)
{
return ("Conversion to string is not implemented");
}
}
struct BinaryNumeral
{
private int value;
public BinaryNumeral(int value) //constructor
{
this.value = value;
}
static public implicit operator BinaryNumeral(int value)
{
return new BinaryNumeral(value);
}
static public explicit operator int(BinaryNumeral binary)
{
return (binary.value);
}
static public implicit operator string(BinaryNumeral binary)
{
return ("Conversion to string is not implemented");
}
}
class TestConversions
{
static void Main()
{
RomanNumeral roman;
BinaryNumeral binary;
roman = 10;
// Perform a conversion from a RomanNumeral to a BinaryNumeral:
binary = (BinaryNumeral)(int)roman;
// Perform a conversion from a BinaryNumeral to a RomanNumeral:
// No cast is required:
roman = binary;
System.Console.WriteLine((int)binary);
System.Console.WriteLine(binary);
// Keep the console window open in debug mode.
System.Console.WriteLine("Press any key to exit.");
System.Console.ReadKey();
}
}
/* Output:
10
Conversion not yet implemented
*/
可靠编程
在上面的示例中，语句：
binary = (BinaryNumeral)(int)roman;执行从 RomanNumeral 到 BinaryNumeral 的转换。由于没有从 RomanNumeral 到 BinaryNumeral 的直接转换，所以使用一个转换将 RomanNumeral 转换为 int，并使用另一个转换将 int 转换为 BinaryNumeral。
另外，语句
roman = binary;执行从 BinaryNumeral 到 RomanNumeral 的转换。由于 RomanNumeral 定义了从 BinaryNumeral 的隐式转换，所以不需要转换。