PowerShell - Password Generator - How to always include number in string?

You could invoke the Get-Random cmdlet three times, each time with a different input parameter (punc, digit and letters), concat the result strings and shuffle them using another Get-Random invoke:

 (Get-Random -Count 15 -InputObject ([char[]]$yourPassword)) -join ''

However, why do you want to reinvent the wheel? Consider using the following GeneratePassword function:

[Reflection.Assembly]::LoadWithPartialName("System.Web")
[System.Web.Security.Membership]::GeneratePassword(15,2)

And to ensure, it contains at least one random number (you already specify the number of symbols):

do {
   $pwd = [System.Web.Security.Membership]::GeneratePassword(15,2)
} until ($pwd -match '\d')

As suggested by jisaak, there is no 100% guaranty that the Membership.GeneratePassword Method generates a password that meets the AD complexity requirements.

That's why I reinvented the wheel:

Function MakeUp-String([Int]$Size = 8, [Char[]]$CharSets = "ULNS", [Char[]]$Exclude) {
    $Chars = @(); $TokenSet = @()
    If (!$TokenSets) {$Global:TokenSets = @{
        U = [Char[]]'ABCDEFGHIJKLMNOPQRSTUVWXYZ'                                #Upper case
        L = [Char[]]'abcdefghijklmnopqrstuvwxyz'                                #Lower case
        N = [Char[]]'0123456789'                                                #Numerals
        S = [Char[]]'!"#$%&''()*+,-./:;<=>?@[\]^_`{|}~'                         #Symbols
    }}
    $CharSets | ForEach {
        $Tokens = $TokenSets."$_" | ForEach {If ($Exclude -cNotContains $_) {$_}}
        If ($Tokens) {
            $TokensSet += $Tokens
            If ($_ -cle [Char]"Z") {$Chars += $Tokens | Get-Random}             #Character sets defined in upper case are mandatory
        }
    }
    While ($Chars.Count -lt $Size) {$Chars += $TokensSet | Get-Random}
    ($Chars | Sort-Object {Get-Random}) -Join ""                                #Mix the (mandatory) characters and output string
}; Set-Alias Create-Password MakeUp-String -Description "Generate a random string (password)"

Usage:

• The Size parameter defines the length of the password.
• The CharSets parameter define the complexity where the character U, L, N and S stands for Uppercase, Lowercase, Numerals and Symbols. If supplied in lowercase (u, l, n or s) the returned string might contain any of character in the concerned character set, If supplied in uppercase (U, L, N or S) the returned string will contain at least one of the characters in the concerned character set.
• The Exclude parameter lets you exclude specific characters that might e.g. lead to confusion like an alphanumeric O and a numeric 0 (zero).

Examples:

To create a password with a length of 8 characters that might contain any uppercase characters, lowercase characters and numbers:

Create-Password 8 uln

To create a password with a length of 12 characters that that contains at least one uppercase character, one lowercase character, one number and one symbol and does not contain the characters OLIoli01:

Create-Password 12 ULNS "OLIoli01"

_{For the latest Create-Password version, see: https://powersnippets.com/create-password/}

Command to Generate Random passwords by using existing funciton:

[system.web.security.membership]::GeneratePassword(x,y)

x = Length of the password
y = Complexity

General Error:

Unable to find type [system.web.security.membership]. Make sure that the assembly that contains this type is loaded.

Solution:

Run the below command:

Add-Type -AssemblyName System.web;