Check password minimum length - winforms

Question

I'm building my own PowerShell GUI password generator and so far it works. But as I want more control regarding the input I've run into a problem;
verify that the minimum length input is greater than x.
The $NumberBox1 is a textbox where the length of the password is set. And if it is less than 8 it should automatically set it to 8 and generate the password when the button is clicked.
If I change the value in the textbox $NumberBox1 to 9 it works. But not when the value is below 8 or above 9.
It's this section I can't get right:
## Check password length
if ($pw_length -le "7") {
$pw_length = "8"
$NumberBox1.Text = "8"
}
If I comment out the above part I can set any length for the password.
Full code below:
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Drawing")
$form1 = New-Object System.Windows.Forms.Form
$form1.Text = "Password generator"
$form1.Name = "Password generator"
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 400
$System_Drawing_Size.Height = 200
$form1.ClientSize = $System_Drawing_Size
$NumberBox1 = New-Object System.Windows.Forms.TextBox
$NumberBox1.Location = New-Object System.Drawing.Size(110,20)
$NumberBox1.Size = New-Object System.Drawing.Size(50,25)
$NumberBox1.Text = "12"
$InfoBox1 = New-Object System.Windows.Forms.Label
$InfoBox1.Location = New-Object System.Drawing.Size(20,23)
$InfoBox1.Size = New-Object System.Drawing.Size(150,25)
$InfoBox1.Text = "Password length:"
$InfoBox3 = New-Object System.Windows.Forms.Label
$InfoBox3.Location = New-Object System.Drawing.Size(170,24)
$InfoBox3.Size = New-Object System.Drawing.Size(180,25)
$InfoBox3.Text = "Minimum length is always set to 8"
$TextBox1 = New-Object System.Windows.Forms.TextBox
$TextBox1.Location = New-Object System.Drawing.Size(200,140)
$TextBox1.Size = New-Object System.Drawing.Size(150,25)
$generate = New-Object System.Windows.Forms.Button
$generate.Location = New-Object System.Drawing.Size(20,140)
$generate.Size = New-Object System.Drawing.Size(150,22)
$generate.Text = "Generate password"
$InfoBox2 = New-Object System.Windows.Forms.Label
$InfoBox2.Location = New-Object System.Drawing.Size(20,165)
$InfoBox2.Size = New-Object System.Drawing.Size(360,25)
$generate.Add_Click({
$pw_length = $NumberBox1.Text
## Check password length
if ($pw_length -lt "7") {
$pw_length = "8"
$NumberBox1.Text = "8"
}
## Password with letters, numbers and punctiation
$PW_F = ([char[]](Get-Random -Input $(33..93 + 95 + 97..122) -Count $pw_length)) -join ""
$TextBox1.Text = $pw_F
$InfoBox2.Text = "Full complexity used. Length: $pw_length"
})
$form1.Controls.Add($generate)
$form1.Controls.Add($NumberBox1)
$form1.Controls.Add($TextBox1)
$form1.Controls.Add($InfoBox1)
$form1.Controls.Add($InfoBox2)
$form1.Controls.Add($InfoBox3)
$form1.Add_Shown({$form1.Activate()})
[void] $form1.ShowDialog()

Answer 1

Your $pw_length contains a string. For your -lt operation, you need it to be an integer.
Solution: Cast your variable like this.
[int]$pw_length = $NumberBox1.Text
or
$pw_length = $NumberBox1.Text -as [int]

Answer 2

You can use the [math]::max function, so no if required (intrinsic casting):
$generate.Add_Click( {
$pw_length = [math]::max($NumberBox1.Text,8)
$NumberBox1.Text = $pw_length
## Password with letters, numbers and punctiation
$PW_F = ([char[]](Get-Random -Input $(33..93 + 95 + 97..122) -Count $pw_length)) -join ""
$TextBox1.Text = $pw_F
$InfoBox2.Text = "Full complexity used. Length: $pw_length"
})