Display the date in textbox powershell forms - forms

Question

I am writing a script to get the data from user input as date, when I select another date it is not displaying in text box, please suggest where is the issue
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Drawing")
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
$Form = New-Object System.Windows.Forms.Form
$Form.Size = New-Object System.Drawing.Size(800,600)
$Form.Text = "test"
$Form.FormBorderStyle = "FixedDialog"
$TextBoxlabel = New-Object System.Windows.Forms.Label
$TextBoxlabel.Location = New-Object System.Drawing.Point(10,50)
$TextBoxlabel.Size = New-Object System.Drawing.Size(100,20)
$TextBoxlabel.Text = 'Input No:'
$form.Controls.Add($TextBoxlabel)
$TextBox = New-Object System.Windows.Forms.TextBox
$TextBox.Location = New-Object System.Drawing.Size(120,50)
$TextBox.Size = New-Object System.Drawing.Size(180,20)
$TextBox.MultiLine = $false
$TextBox.ScrollBars = "Vertical"
$Form.Controls.Add($TextBox)
$StartDatelabel = New-Object System.Windows.Forms.Label
$StartDatelabel.Location = New-Object System.Drawing.Point(10,100)
$StartDatelabel.Size = New-Object System.Drawing.Size(100,20)
$StartDatelabel.Text = 'Start Date:'
$form.Controls.Add($StartDatelabel)
$StartDateTextBox = New-Object System.Windows.Forms.TextBox
$StartDateTextBox.Location = New-Object System.Drawing.Size(120,100)
$StartDateTextBox.Size = New-Object System.Drawing.Size(100,20)
$StartDateTextBox.MultiLine = $false
$StartDateTextBox.ScrollBars = "Vertical"
$Form.Controls.Add($StartDateTextBox)
$Button1 = New-Object System.Windows.Forms.Button
$Button1.Location = New-Object System.Drawing.Size(220,100)
$Button1.Size = New-Object System.Drawing.Size(50,20)
$Button1.Text = "Date1"
$Button1.Add_Click({
$StartDateInput = New-Object System.Windows.Forms.MonthCalendar
$StartDateInput.ShowTodayCircle = $false
$StartDateInput.MaxSelectionCount = 1
$StartDateInput.Location = New-Object System.Drawing.Size(120,120)
$StartDateTextBox.Text = $StartDateInput.SelectionStart
$form.Controls.Add($StartDateInput)
})
$Form.Controls.Add($Button1)
$OutputTextBox = New-Object System.Windows.Forms.TextBox
$OutputTextBox.Location = New-Object System.Drawing.Size(10,320)
$OutputTextBox.Size = New-Object System.Drawing.Size(760,200)
$OutputTextBox.MultiLine = $true
$OutputTextBox.ScrollBars = "Vertical"
$OutputTextBox.ReadOnly = $true
$Form.Controls.Add($OutputTextBox)
$Form.Add_Shown({$Form.Activate()})
[void] $Form.ShowDialog()
when I am selecting the date (other than default date) it is not displaying in text box