Check whether CheckBox checked in DataGridView on Button Click in VB.Net

Dear Sir,

I'm Trying to check whether checkbox without checked in datagridview column in event button with vb.net.

So I want if the user only does 1 checkbox that is enough or several checkbox then the messagebox will not appear unless there is no checked at all then the messagebox appears when in event button ("Btncheckforcheckboxdgvunchec")

I tried it in the event button ("Btncheckforcheckboxdgvunchec") 

Not successful messagebox won't appear if I checkbox all

Please Guide me

Thanks

Imports System.Globalization

Public Class Form2
    Private OrderDetail As List(Of OrderDetail)
    Private bindingSource As BindingSource = Nothing
    Private _criteriasBindingList As New SortableBindingList(Of OrderDetail)()
    Public Sub New()
        InitializeComponent()
        Dim CheckedBoxColumn As New DataGridViewCheckBoxColumn
        CheckedBoxColumn.Width = 40
        CheckedBoxColumn.Name = "checkboxcolumn"
        CheckedBoxColumn.HeaderText = "Check"
        CheckedBoxColumn.ReadOnly = False
        DataGridView1.Columns.Insert(0, CheckedBoxColumn)
    End Sub
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.LoadData()
    End Sub
    Private Sub LoadData()
        OrderDetail = New List(Of OrderDetail) From {
            New OrderDetail() With {
                .Invono = "PI0001",
                .InvoDate = Convert.ToDateTime("06-05-2024"),
                .Days = Convert.ToDateTime("06-05-2024").ToString("dddd"),
                .ProductName = "TEST 1000",
                .UnitPrice = 15000,
                .Quantity = 20
            },
            New OrderDetail() With {
                .Invono = "PI0002",
                .InvoDate = Convert.ToDateTime("07-05-2024"),
                .Days = Convert.ToDateTime("07-05-2024").ToString("dddd"),
                .ProductName = "TEST 2000",
                .UnitPrice = 25000,
                .Quantity = 20
            },
            New OrderDetail() With {
                .Invono = "PI0003",
                .InvoDate = Convert.ToDateTime("06-05-2024"),
                .Days = Convert.ToDateTime("06-05-2024").ToString("dddd"),
                .ProductName = "TEST 3000",
                .UnitPrice = 17000,
                .Quantity = 20
            },
            New OrderDetail() With {
                .Invono = "PI0004",
                .InvoDate = Convert.ToDateTime("07-05-2024"),
                .Days = Convert.ToDateTime("07-05-2024").ToString("dddd"),
                .ProductName = "TEST 4000",
                .UnitPrice = 18000,
                .Quantity = 20
            }
        }

        _criteriasBindingList = New SortableBindingList(Of OrderDetail)(OrderDetail)
        bindingSource = New BindingSource With {.DataSource = _criteriasBindingList}
        DataGridView1.DataSource = bindingSource
    End Sub

Private Sub Btncheckforcheckboxdgvunchec_Click(sender As Object, e As EventArgs) Handles Btncheckforcheckboxdgvunchec.Click
        For Each row As DataGridViewRow In DataGridView1.Rows
            Dim cell As DataGridViewCheckBoxCell = TryCast(row.Cells("checkboxcolumn"), DataGridViewCheckBoxCell)
            If cell.Value Is cell.TrueValue Then
                MessageBox.Show("checkboxcolumn must be checked")
                Return
            End If
        Next row
    End Sub
End Class
Public Class OrderDetail
    Public Property Invono As String
    Public Property InvoDate As DateTime
    Public Property Days As String
    Public Property ProductName As String
    Public Property UnitPrice As Integer
    Public Property Quantity As Integer
End Class