public class Rational { protected static Rational one; public static Rational One { get { return one; } } protected static Rational zero; public static Rational Zero { get { return zero; } } { public int N { get; set; } public int M { get; set; } static Rational() { one = new Rational(1, 1); zero = new Rational(0, 1); } public Rational(int n, int m) { N = n; M = m; } public override string ToString() { return string.Format("{0}/{1}", N, M); } } static void Main(string[] args) {? Rational r1 = Rational.One;//r1 is 1/1 Rational r2 = Rational.Zero;//r2 is 0/1 Rational r = new Rational(1, 2);? Rational r3 = Rational.One;//r3 is 1/1? Rational r4 = Rational.Zero;//r4 is 0/1 }?但是: public class Ra { protected static Rational one; public static Rational One { get { return one; } } protected static Rational zero; public static Rational Zero { get { return zero; } } } public class Rational:Ra { public int N { get; set; } public int M { get; set; } static Rational() { one = new Rational(1, 1); zero = new Rational(0, 1); } public Rational(int n, int m) { N = n; M = m; } public override string ToString() { return string.Format("{0}/{1}", N, M); } } ? static void Main(string[] args) {? Rational r1 = Rational.One;//r1 is null? Rational r2 = Rational.Zero;//r2 is null Rational r = new Rational(1, 2);? Rational r3 = Rational.One;//r3 is 1/1? Rational r4 = Rational.Zero;//r4 is 0/1 }字段在類中，靜態(tài)構(gòu)造函數(shù)會(huì)在第一次調(diào)用屬性之前調(diào)用初始化靜態(tài)字段，但是字段繼承于基類，靜態(tài)構(gòu)造不會(huì)在調(diào)用屬性之前初始為，而是在實(shí)例化類之后初始化，什么原因，什么解決辦法？