C# 允许在一个循环中使用另一个循环。下面使用几个例子来说明这个概念。

　　语法

　　C# 中的嵌套for循环语句的语法如下：

for ( init; condition; increment )
{
   for ( init; condition; increment )
   {
      statement(s);
   }
   statement(s);
}12345678复制代码类型：[csharp]

　　C# 中的嵌套while循环语句的语法如下：

while(condition)
{
   while(condition)
   {
      statement(s);
   }
   statement(s);
}12345678复制代码类型：[csharp]

　　C# 中的嵌套do...while循环语句的语法如下：

do
{
   statement(s);
   do
   {
      statement(s);
   }while( condition );

}while( condition );123456789复制代码类型：[csharp]

　　可以将任何类型的循环放在任何其他类型的循环中。例如，for循环可以在while循环内，反之亦然。

　　示例

　　以下程序使用嵌套for循环来查找从2到100内的素数：

using System;
namespace Loops
{
   class Program
   {
      static void Main(string[] args)
      {
         /* local variable definition */
         int i, j;
         for (i = 2; i < 100; i++)
         {
            for (j = 2; j <= (i / j); j++)
            if ((i % j) == 0) break; // if factor found, not prime
            if (j > (i / j))
            Console.WriteLine("{0} is prime", i);
         }
         Console.ReadLine();
      }
   }
}1234567891011121314151617181920复制代码类型：[csharp]

　　当编译和执行上述代码时，会产生以下结果：

2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime

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