PowerShell输入框，不允许空白条目

Question

我有以下输入弹出框代码（http://technet.microsoft.com/library/dn792463.aspx）

Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
$form = New-Object System.Windows.Forms.Form 
$form.Text = "PoliceWorks Version Number"
$form.Size = New-Object System.Drawing.Size(300,200) 
$form.StartPosition = "CenterScreen"
$OKButton = New-Object System.Windows.Forms.Button
$OKButton.Location = New-Object System.Drawing.Point(75,120)
$OKButton.Size = New-Object System.Drawing.Size(75,23)
$OKButton.Text = "OK"
$OKButton.DialogResult = [System.Windows.Forms.DialogResult]::OK
$form.AcceptButton = $OKButton
$form.Controls.Add($OKButton)
$CancelButton = New-Object System.Windows.Forms.Button
$CancelButton.Location = New-Object System.Drawing.Point(150,120)
$CancelButton.Size = New-Object System.Drawing.Size(75,23)
$CancelButton.Text = "Cancel"
$CancelButton.DialogResult = [System.Windows.Forms.DialogResult]::Cancel
$form.CancelButton = $CancelButton
$form.Controls.Add($CancelButton)
$label = New-Object System.Windows.Forms.Label
$label.Location = New-Object System.Drawing.Point(10,20) 
$label.Size = New-Object System.Drawing.Size(280,20) 
$label.Text = "Please enter the information in the space below:"
$form.Controls.Add($label) 
$textBox = New-Object System.Windows.Forms.TextBox 
$textBox.Location = New-Object System.Drawing.Point(10,40) 
$textBox.Size = New-Object System.Drawing.Size(260,20) 
$form.Controls.Add($textBox) 
$form.Topmost = $True
$form.Add_Shown({$textBox.Select()})
$result = $form.ShowDialog()
if ($result -eq [System.Windows.Forms.DialogResult]::OK)
{
$x = $textBox.Text
$x
}

使用此脚本，我可以在弹出窗口中输入空白数据。如何阻止/限制角色数量。

Answer 1

if (!$length)将捕获0长度输入。这是因为 [bool]$null= false和[bool]'' = false。 !是-not的别名。