DataGridView for循环错误

Question

考虑以下代码：

Public Class CrewDatabaseForm

Public Shared CrewList As List(Of String)

Private Sub CrewDatabaseForm_FormClosed(sender As Object, e As FormClosedEventArgs) Handles Me.FormClosed
    Dim CL As New List(Of String)
    If DataGridView1.Rows.Count = 2 Then CL.Add(DataGridView1.Rows(0).Cells(0).Value)
    If DataGridView1.Rows.Count > 2 Then
        For i As Integer = 0 To (DataGridView1.Rows.Count - 2)
            CL.Add(DataGridView1.Rows(i).Cells(0).Value.ToString)
        Next
    End If
    MessageBox.Show(DataGridView1.Rows.Count.ToString)


End Sub


Private Sub CrewDatabaseForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load

End Sub

结束班

- 此表单只是一个datagridview。每当我退出表单，if和for语句开始时，如果我在第一列中输入了一个值而未按下则输入错误：

“Stage Tally.exe中发生了'System.NullReferenceException'类型的异常，但未在用户代码中处理

附加信息：未将对象引用设置为对象的实例。

如果存在此异常的处理程序，则可以安全地继续该程序。“