如何将PHP代码转换为vb.net for循环

how do i convert this php code to vb im trying to do this in .net but the value is only 1 value what is the code of .net using my php codes

this is my code in php

              $ctr = 7 
              for ($i = 0;$i < $ctr;$i++) 
                { 
                    $prenum .= '0';
                } 

output = 0000000

    Dim prenum as string = "0"
    Dim ctr as Integer = 7
    For i = 0 To ctr
        output = prenum
    Next

output = 0

the operator '.' in php concatenates strings, the operator for vb to concatenate is '&'...

Dim prenum as string = "0"
Dim ctr as Integer = 7
For i = 0 To ctr
    output = output & prenum
Next