C# 流程控制（学习笔记3）

1.条件语句

public void Test3(){int a = 1; int b = 2;int c = a + b;if (c > 0){MessageBox.Show(c.ToString());}else if (c == 0){MessageBox.Show("c=0");}else{MessageBox.Show("c<0");}          }

2.选择语句和循环语句

        public void Test4(){int[] a = { 1,2,3,0,-10};for (int i = 0; i < a.Length; i++){switch (a[i]){case 1:MessageBox.Show("1");break;case 2:MessageBox.Show("2");break;case 3:MessageBox.Show("3");break;default:MessageBox.Show("other");break;}}}

3. while

        public void Test5(){int[] a = { 1, 2, 3, 0, -10 };for (int i = 0; i < a.Length; i++){while (a[i] < 0){MessageBox.Show("a<0");}}}

4. do...while

        public void Test6(){int[] a = { 1, 2, 3, 0, -10 };for (int i = 0; i < a.Length; i++){do{MessageBox.Show("a<0");} while (a[i] < 0);}}

5. for...each

遍历一个集合

        public void Test7(){int[] a = { 1, 2, 3, 0, -10 };foreach (var i in a){MessageBox.Show(i.ToString());}}

6. break

跳出循环体

        public void Test8(){int[] a = { 1, 2, 3, 0, -10 };foreach (var i in a){if (i < 1){break; //跳出循环}}}

7. continue

跳过后面的代码，从循环体开始处重新执行

        public void Test9(){int[] a = { 1, 2, 3, 0, -10 };foreach (var i in a){if (i < 1){continue; // 后面的代码不再执行，从循环开始处重新执行。MessageBox.Show(i.ToString()); }}}

7. return

退出函数或方法，有返回值就返回。

        public void Test10(){int[] a = { 1, 2, 3, 0, -10 };foreach (var i in a){if (i < 1){return; // 无返回值}}}

        public int Test11(){int[] a = { 1, 2, 3, 0, -10 };foreach (var i in a){if (i < 1){return i; // 有返回值}}return 0;}