C#关键字,explicit和implicit

public static implicit operator float(Currency value)
{
return value.dollars + (value.cents / 100.0f);
}

public static explicit operator Currency(float value)
{
checked
{
uint dollars = (uint)value;
ushort cents = Convert.ToUInt16((value - dollars) * 100);
return new Currency(dollars, cents);
}
}

public static implicit operator float(Currency value)
表示Currency到float是隐式转换，如：
Currency a;
float b = a;

public static explicit operator Currency(float value)
表示float到Currency需要强制转换，如：
float a;
Currency b = (Currency)a;