我对您的代码做了一些调整。

• 我已将您的函数StartProgressBar重命名为Update-ProgressBar，因为它将在每个计时器节拍上被调用以更新状态栏，所以我认为这个名称更不言自明
• 该按钮现在仅用于重新-在需要时启动进度条。
• 您不需要计数器$i，因为ProgressBar对象本身具有跟踪其当前值所需的所有属性。此外，如果您确实需要在函数(和其他脚本块)中使用计数器，则需要使用$script:i对其进行寻址。没有该脚本作用域，$i就不存在。
• 要使进度条在启动时开始运行，您需要使用$Form.Add_Shown({$timer.Enabled = $true; $timer.Start()})启用和启动计时器
• 要在其他窗口顶部显示该窗体，请设置$Form.Topmost = $true

代码如下：

function Update-ProgressBar {
    # this function will be called on every timer tick
    $pbrTest.PerformStep()
    $progressLabel.Text = "VALUE EQ $($pbrTest.Value)%"
    if ($pbrTest.Value -ge $pbrTest.Maximum) {
        $timer.Enabled = $false
        $timer.Stop()
        $btnRestart.Enabled = $true
    }
}
$Form = New-Object System.Windows.Forms.Form
$Form.Width = 400
$Form.Height = 200
$Form.Text = "Add Resource"
$Form.Topmost = $true  # place this form on top
# Init ProgressBar
$pbrTest = New-Object System.Windows.Forms.ProgressBar
$pbrTest.Location = New-Object System.Drawing.Point(10,10)
$pbrTest.Size = New-Object System.Drawing.Size(100,50)
$pbrTest.Maximum = 100
$pbrTest.Minimum = 0
$pbrTest.Value = 0
$pbrTest.Step = 1
$Form.Controls.Add($pbrTest)
# Button
$btnRestart = New-Object System.Windows.Forms.Button
$btnRestart.Location = New-Object System.Drawing.Size(120,10)
$btnRestart.Size = New-Object System.Drawing.Size(100,30)
$btnRestart.Text = "Restart Progress"
$btnRestart.Enabled = $false  # disabled at first
$btnRestart.Add_Click({ 
    # disable this button while the progressbar is running
    $this.Enabled = $false  
    # reset the progressbar to value 0 and start the timer
    $pbrTest.Value = 0
    $timer.Enabled = $true
    $timer.Start()
})
$Form.Controls.Add($btnRestart)
# Label
$progressLabel = New-Object System.Windows.Forms.Label
$progressLabel.Size = '370, 20'
$progressLabel.Location = '10,70'
$progressLabel.Text = "Processing..."
$Form.Controls.Add($progressLabel)
# Timer
$timer = New-Object System.Windows.Forms.Timer 
$timer.Interval = 50
$timer.Enabled = $false  # disabled at first
$timer.Add_Tick({ Update-ProgressBar })
# start the timer as soon as the form is shown
$Form.Add_Shown({$timer.Enabled = $true; $timer.Start()})
# Show Form
$Form.ShowDialog()
# stop the timer and dispose of it and finally also dispose of the form
$timer.Stop()
$timer.Dispose()
$pbrTest.Dispose()
$Form.Dispose()

我认为如果您删除onClick事件，它将自动运行，但我不知道这是否明显。

Function StartProgressBar
{
    if($i -le 5){
        $pbrTest.Value = $i
        $script:i += 1
    }
    else {
        $timer.enabled = $false
    }   
}
$Form = New-Object System.Windows.Forms.Form
$Form.width = 400
$Form.height = 200
$Form.Text = "Add Resource"
# Init ProgressBar
$pbrTest = New-Object System.Windows.Forms.ProgressBar
$pbrTest.Maximum = 100
$pbrTest.Minimum = 0
$pbrTest.Location = new-object System.Drawing.Size(10,10)
$pbrTest.size = new-object System.Drawing.Size(100,50)
$i = 0
$Form.Controls.Add($pbrTest)
# Button
$btnConfirm = new-object System.Windows.Forms.Button
$btnConfirm.Location = new-object System.Drawing.Size(120,10)
$btnConfirm.Size = new-object System.Drawing.Size(100,30)
$btnConfirm.Text = "Start Progress"
$Form.Controls.Add($btnConfirm)
$timer = New-Object System.Windows.Forms.Timer 
$timer.Interval = 1000
$timer.add_Tick({
StartProgressBar
})
$timer.Enabled = $true
$timer.Start()
# Button Click Event to Run ProgressBar
While ($i -le 100) {
    $pbrTest.Value = $i
    Start-Sleep -m 1
    "VALLUE EQ"
    $i
    $i += 1
}
# Show Form
$Form.Add_Shown({$Form.Activate()})
$Form.ShowDialog()