if/else语句中的语法错误

Question

我对c＃非常陌生，并且在处理基本程序时收到此错误（错误只能将赋值，调用，递增，递减，等待和新对象表达式用作声明），并无法弄清楚它出现的原因。

if (pizzaDiameter >= 12 && pizzaDiameter < 16)// begin nested if statement 
{ 
    Console.WriteLine("A" + pizzaDiameter + "will yield 8 slices."); 
} 
else if (pizzaDiameter >= 16 && pizzaDiameter < 24)//Second pizza diameter range 
{ 
    Console.WriteLine("A" + pizzaDiameter + "will yield 12 slices."); 
} 
else if (pizzaDiameter >= 24 && pizzaDiameter < 30) 
{ 
    Console.WriteLine("A" + pizzaDiameter + "will yield 16 slices."); 
} 
else (pizzaDiameter >= 24 && pizzaDiameter <= 30) 
{ 
    Console.WriteLine("A" + pizzaDiameter + "will yield 24 slices."); 
} 
else // pizza diameter was not a whole number 
{ 
    Console.WriteLine("Pizza diameter must be between 12-36 inclusive.");// Error appears here. 
} 
else //pizza diameter must be between 12-36 
{ 
    Console.WriteLine("Pizza diameter must be a whole number."); 
} 

Answer 1

有一些问题与您的控制结构，即你得只有一个if()，而是三次else。

另外，尽量去想问题，你会发现，你可以显著简化了整体结构（也跳过许多检查）：

if (pizzaDiameter < 12) // All diameters below 12 will use this branch. 
    Console.WriteLine("Your pizza seems to be too small."); 
else if (pizzaDiameter < 16) // You don't have to ensure it's bigger than 12, since those smaller already picked the branch above. 
    Console.WriteLine("A diameter of " + pizzaDiameter + " will yield 8 slices"); 
else if (pizzaDiameter < 24) // Again you won't have to care for less than 16. 
    Console.WriteLine("A diameter of " + pizzaDiameter + " will yield 12 slices"); 
// ... 
else 
    Console.WriteLine("Your pizza seems to be too big.");