VB.Net - 嵌套循环
VB.Net 允许在另一个循环中使用一个循环。 以下部分显示了一些示例来说明该概念。
语法
VB.Net 中嵌套 For 循环语句的语法如下 −
For counter1 [ As datatype1 ] = start1 To end1 [ Step step1 ]
For counter2 [ As datatype2 ] = start2 To end2 [ Step step2 ]
...
Next [ counter2 ]
Next [ counter 1]
VB.Net 中嵌套 While 循环 语句的语法如下 −
While condition1
While condition2
...
End While
End While
VB.Net 中嵌套 Do...While 循环 语句的语法如下 −
Do { While | Until } condition1
Do { While | Until } condition2
...
Loop
Loop
关于循环嵌套的最后一点是，您可以将任何类型的循环放在任何其他类型的循环内。 例如，for 循环可以位于 while 循环内，反之亦然。
示例
下面的程序使用嵌套的 for 循环来查找 2 到 100 之间的素数 −
Module loops
Sub Main()
' 局部变量定义
Dim i, j As Integer
For i = 2 To 100
For j = 2 To i
' if factor found, not prime
If ((i Mod j) = 0) Then
Exit For
End If
Next j
If (j > (i \ j)) Then
Console.WriteLine("{0} is prime", i)
End If
Next i
Console.ReadLine()
End Sub
End Module
当上面的代码被编译并执行时，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
