vbs inputbox mandatory text [duplicate] - validation

Question

When I run the following snippet, and enter an acceptable value, I get the desired result.
do while len(strselect) = 0 'or strselect<>"1" or strselect<>"2" or strselect<>"3"
strselect = inputbox ("Please select:" &vbcrlf&vbcrlf&_
"1. Add an entry" &vbcrlf&vbcrlf&_
"2. Remove an entry" &vbcrlf&vbcrlf&_
"3. Search for an entry" &vbcrlf, "Contact Book")
if isempty(strselect) then
wscript.quit()
elseif strselect="1" then
wscript.echo "You chose 1"
elseif strselect="2" then
wscript.echo "You chose 2"
elseif strselect="3" then
wscript.echo "You chose 3"
end if
loop
However if I try constrain the validation process further (by including the remark in the do while conditions), and run the snippet again, I get the corresponding if condition triggered, but the do loop continues, instead of exiting.
I've tried using isnumeric and cstr on the do loop strselect conditions, with no joy... What am I missing to get the darn thing to exit the loop?

Answer 1

You have a problem with the logic in the condition
condition 1 condition 2 condition 3 condition 4
v----------------v v------------v v------------v v............v
do while len(strselect) = 0 or strselect<>"1" or strselect<>"2" or strselect<>"3"
Depending on value inside strselect, you have
value c1 c2 c3 c4
len=0 <>"1" <>"2" <>"3" c1 or c2 or c3 or c4
-------------------------------------- --------------------
empty true true true true true
1 false false true true true
2 false true false true true
3 false true true false true
other false true true true true
In each line you have at least one condition evaluated as true, and as you are concatenating the conditions with Or operators (evaluate to true if at least one of the values is true), the full condition is evaluated as true and the code keeps looping
You only need to change the condition
Do While strselect<>"1" And strselect<>"2" And strselect<>"3"
Do While Not (strselect="1" Or strselect="2" Or strselect="3")
....