在datagridview中更新数据时，垂直滚动条无法正常工作

Question

当我更新DataGridView中的数据时，垂直滚动条无法正常工作。

加载所有数据后，不显示垂直滚动条向上和向下按钮。我无法滚动垂直滚动条。

以下是更新代码：

private void Form1_Load(object sender, EventArgs e)
{
    dataGridView1.AllowUserToAddRows = false;

    dataGridView1.Columns.Add("StudentId", "Student Id");
    dataGridView1.Columns.Add("StudentName", "Student Name");
    dataGridView1.Columns.Add("StudentCNIC", "Student CNIC");
    dataGridView1.Columns.Add("StudentDoB", "Student DoB");
}

private void button1_Click(object sender, EventArgs e)
{
    Thread trd = new Thread(this.threadtask);
    trd.IsBackground = true;
    trd.Start();   
}

public void threadtask()
{
    OleDbConnection connect = new OleDbConnection();
    connect.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:/Users/Obaid Abbasi/Documents/Students1.accdb;Persist Security Info=False;";
    connect.Open();

    OleDbCommand command = new OleDbCommand();
    command.Connection = connect;
    command.CommandText = "SELECT * From Students";

    OleDbDataReader reader = command.ExecuteReader();

    while (reader.Read())
    {
        dataGridView1.AllowUserToAddRows = false;

        dataGridView1.Rows.Add();
        dataGridView1.ReadOnly = true;

        dataGridView1.Rows[dataGridView1.Rows.Count - 1].Cells[0].Value = reader[0].ToString();
        dataGridView1.Rows[dataGridView1.Rows.Count - 1].Cells[1].Value = reader[1].ToString();
        dataGridView1.Rows[dataGridView1.Rows.Count - 1].Cells["StudentCNIC"].Value = reader[2].ToString();
        dataGridView1.Rows[dataGridView1.Rows.Count - 1].Cells["StudentDoB"].Value = reader[3].ToString();
        Thread.Sleep(100);
    }

    connect.Close();
}

我使用后台线程并在每条记录之间休眠，因为我想在1秒后添加每一行。