How to get checked items from dialog's listview in vb.net

Hello I'm using below code to get checked items but it gives "Object reference not set to instance of object" error. Does anyone knows how can i fix that?

            Try
                If BuildSetLabelID.ShowDialog() = DialogResult.OK Then
                    Dim id As String = BuildSetLabelID.cboSetID.SelectedItem.ToString
                    For Each i As ListViewItem In BuildSetLabelID.lstDataGridViews.CheckedItems
                        MsgBox(i.Name)
                    Next
                 End If
            Catch ex As Exception
                Tools.OutputLog.Print(Tools.OutputLog.Type.ERR, ex.Message)
            End Try

Select allOpen in new window

and this is entire class of dialog

Public Class BuildSetLabelID
    Private Sub OK_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK_Button.Click
        Me.DialogResult = System.Windows.Forms.DialogResult.OK
        Me.Close()
    End Sub

    Private Sub Cancel_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cancel_Button.Click

        Me.DialogResult = System.Windows.Forms.DialogResult.Cancel
        Me.Close()
    End Sub

    Private Sub DialogLoad(sender As Object, e As EventArgs) Handles MyBase.Load
        lstDataGridViews.Clear()
        FindDataGridViews(GUI.pnlModuleBuildContent)
    End Sub
    Private Sub FindDataGridViews(ByVal control As Control)
        If control.HasChildren Then
            For Each childControl As Control In control.Controls
                If (TypeOf (childControl) Is DataGridView) Then
                    Dim dgv As DataGridView = CType(childControl, DataGridView)
                    If dgv.Columns.Contains("colKey") = True Then
                        Dim item As New ListViewItem With {
                        .Text = dgv.Tag,
                        .Tag = dgv.Name
                    }
                        lstDataGridViews.Items.Add(dgv.Tag)
                    End If
                Else
                    FindDataGridViews(childControl)
                End If
            Next
        End If
    End Sub
End Class

Select allOpen in new window