C#基础（4）——break语句、continue语句、while循环、do-while循环、for循环、foreach循环

break、while

break是跳出当前循环，不是所有循环。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{
int i = 1;
int j = 1;
while (i <= 10)
{
while (j <= 10)
{
Console.WriteLine("我是最里层");
j++;
break;
}
Console.WriteLine("我是最外层----");
i++;
}
Console.ReadKey();
}
}
}

但是，break不单独使用，而与if配合使用，当满足一定条件就不再循环了。如：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{
string answer = "n";
int i = 1;
while (answer == "n" && i <= 10)
{
Console.WriteLine("这是第{0}次讲解，你会了吗？y/n", i);
answer = Console.ReadLine();
if (answer == "y")
{
Console.WriteLine("你终于会了！放学了。。。");
break;
}

i++;
}
if (i == 11)
{
Console.WriteLine("还不会，第{0}次了！放弃吧！", i-1);
}
Console.ReadKey();
}
}
}

continue

do-while循环

先执行一遍，再拿执行后的结果，再循环的，推荐do-while，即先做再判断：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{
string input = "n";
do
{
if (input != "n")
{
Console.WriteLine("要输入n");
}
Console.WriteLine("y/n?");
input = Console.ReadLine();

} while (input == "n"||input!="y");
Console.ReadKey();
}
}
}

for循环

打for顺序循环双击tab，代码格式化输出。

打forr逆序循环双击tab，代码格式化输出。

变步长：for (int i = 0; i < 100; i+=2)

求水仙花数：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{
int hundred = 0;
int decade = 0;
int unit = 0;

for (int i = 100; i <= 999; i++)
{
hundred = i / 100;
decade = i % 100 / 10;
unit = i % 10;
if (Math.Pow(hundred, 3) + Math.Pow(decade, 3) + Math.Pow(unit, 3) == i)
{
Console.WriteLine("水仙花数为：{0}", i);
}
}
Console.ReadKey();
}
}
}

九九乘法表

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{

for (int i = 1; i <= 9; i++)
{
for (int j = 1; j <=9; j++)
{
Console.Write("{0}*{1}={2}\t", i, j,i * j);
}
Console.WriteLine();
}
Console.ReadKey();
}
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{

for (int i = 1; i <= 9; i++)
{
for (int j = 1; j <=i; j++)
{
Console.Write("{0}*{1}={2}\t", i, j,i * j);
if (i == j)
{
Console.WriteLine();
}
}

}
Console.ReadKey();
}
}
}

质数

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ChuangzhiConsel
{
class Program
{
static void Main(string[] args)
{
//怎么判断质数（素数）
Console.WriteLine("输入大于2的数字：");
int length = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("质数：1");
for (int i = 2; i <= length; i++)
{
bool is_prime = true;
for (int j = 2; j < i; j++)
{
if (i % j == 0)
{
is_prime = false;
break;//不是质数
}
}
if (is_prime)
{
Console.WriteLine("质数：{0}", i);
}
}

Console.ReadKey();

}
}
}