regex - validation pattern in ValidationExpression of asp.net webform: required at least one digit -

so have validate pattern support lower , upper case character , must have at least 1 digit, must between range of 8 16.

so far have

validationexpression="(^[a-za-z0-9](?=.*\d){8,16})$"

that seems not working, hint ?

i.e.

abcdef not work  abcdef12 work

the problem:

(^[a-za-z0-9](?=.*\d){8,16})$

this looking match within string that:
- contains single item out of [a-za-z0-9]
- has look-ahead of .*\d, lookahead hapening8-16 times.

possible solutions:

put {8,16} on [a-za-z0-9] rather look-ahead, , move look-ahead front:

^(?=.*\d)[a-za-z0-9]{8,16}$

also, if wish have atleast 1 of each capital , lowercase letters, can this:

^((?=.*\d)(?=.*[a-z])(?=.*[a-z])[a-za-z0-9]{8,16})$

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