与for和while循环不同，for循环在循环开始时测试循环条件，do.while循环在循环结束时检查其条件。
do.while循环类似于while循环，不同之处在于do.while循环保证至少执行一次。
do...while - 语法
C#中do.while循环的语法是-
do { statement(s); } while( condition );
do...while - 流程图
using System;
namespace Loops {
class Program {
static void Main(string[] args) {
/* 局部变量定义 */
int a = 10;
</span><span class="com">/* do循环执行 */</span><span class="pln">
</span><span class="kwd">do</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="typ">Console</span><span class="pun">.</span><span class="typ">WriteLine</span><span class="pun">(</span><span class="str">"value of a: {0}"</span><span class="pun">,</span><span class="pln"> a</span><span class="pun">);</span><span class="pln">
a </span><span class="pun">=</span><span class="pln"> a </span><span class="pun">+</span><span class="pln"> </span><span class="lit">1</span><span class="pun">;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="kwd">while</span><span class="pln"> </span><span class="pun">(</span><span class="pln">a </span><span class="pun"><</span><span class="pln"> </span><span class="lit">20</span><span class="pun">);</span><span class="pln">
</span><span class="typ">Console</span><span class="pun">.</span><span class="typ">ReadLine</span><span class="pun">();</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
}
}
编译并执行上述代码时，将生成以下输出-
value of a: 10 value of a: 11 value of a: 12 value of a: 13 value of a: 14 value of a: 15 value of a: 16 value of a: 17 value of a: 18 value of a: 19
