Evaluate the number of all prime numbers within n

Private sub llstart_linkclicked (byval sender as system. Object, byval e _
System. Windows. Forms. linklabellinkclickedeventargs )_
Handles llstart. linkclicked
If isnumeric(me.txt maxnbr. Text) = false then
Msgbox ("Max NBR must be numeric! ",_
Msgboxstyle. Exclamation ,_
"Max NBR not numeric ")
Return
End if

Dim N, I, j
N = cint(me.txt maxnbr. Text)

Dim Z (N)
Dim starttime as datetime = now

'Initialize Array
For I = 0 to n
Z (I) = 0
Next

'Mark multiples of I

For I = 2 to n/2
For J = 2 * I to N step I
Z (j) = 1
Next
Next

'Count unmarked numbers, which are primes
Dim NBR = 0

For I = 2 to n
If Z (I) = 0 then
NBR + = 1
End if
Next

Dim TS as new timespan (now. ticks-starttime. ticks)

Me. lblnbrprimes. Text = NBR
Me. lbltime. Text = ts. tostring

End sub

Reply: this silly Code strengthened my confidence in VB. NET.

For I = 2 to n/2
For J = 2 * I to N step I
Z (j) = 1
Next
Next

This algorithm is used to traverse the number I from 2 to n/2. For each I, set all its multiples in array Z to 1. In fact, this Z can be expressed in the bool type. 1 is the sum, and 0 is the prime number.
For I = 2 to n
If Z (I) = 0 then
NBR + = 1
End if
Next
Traverse Z and NBR to write down the total number of prime numbers.
See the original algorithm: http://www.math.utah.edu/classes/216/assignment-07.html
This algorithm is indeed excellent. Its algorithm Z (j) = 1 indicates that the number of execution steps is X, and X indicates the number of all units smaller than N. Obviously, x <= n.